Rhoda Karpatkin, who pressed for painstaking product testing for safety and quality while promoting comparison shopping for value during more than four decades at Consumers Union as counsel, executive director and president, died on Friday at her home in Manhattan. She was 93.

The cause was brain cancer, her daughter, Deborah Karpatkin, said.

Ms. Karpatkin, a New York lawyer and civil rights advocate, had served for 16 years as the nonprofit organization’s counsel when she was selected in 1974 as executive director, the first woman to hold that position. Consumers Union, the publisher of Consumer Reports, later changed its name to Consumer Reports.

“Rhoda led CR to become the trusted name and consumer champion we are today,” Marta L. Tellado, the president and chief executive of Consumer Reports, said in a statement.

In 1993, Lear’s magazine called Ms. Karpatkin “the nation’s smartest shopper.”

Under her leadership, subscriptions to the magazine, which accepts no paid advertising, more than doubled, to 4.3 million, and in 2000, the organization created what was then the largest pay website, with 350,000 subscribers. Ms. Karpatkin also raised $40 million to build a new headquarters in Yonkers, N.Y., and an automobile testing track.

The organization notably “used its product safety expertise to publicize safety hazards, advise regulators, and communicate with Congress,” according to “Watchdogs and Whistleblowers: A Reference Guide to Consumer Activism” (2015), by Stephen Brobeck and Robert N. Mayer.

“Rhoda combined an unwavering passion for the little guy with a smart, strategic sense of how to effect change,” said Kimberly Kleman, a former editor of Consumer Reports. “Working for and with Rhoda was more than a job — it was a mission.”

She added, “It’s also important to recognize that Rhoda was one of the first modern-day publishers who believed that people would pay for content they considered valuable — you didn’t have to give it away, or undervalue it.”

Consumer Reports, which rates and compares products, prides itself on editorial independence and is supported by grants and donations as well as subscriptions.

Since the organization’s founding in 1936, it had never lost or had to settle a lawsuit related to a product review or comparison or assessment, said Barrie Rosen, a spokeswoman.

After Ms. Karpatkin was elevated to executive director, the organization’s board was divided over whether it should continue to focus on product testing or leverage its prestige to lobby for product safety and other legislative and regulatory reforms.

Ms. Karpatkin and Betty Furness, a board member and former New York City consumer affairs commissioner, believed Consumers Union could do both. The consumer advocate Ralph Nader, then a member of the board, split with the group, arguing that it should concentrate on effecting change.

The organization struggled during the Reagan administration, its revenues pummeled by a weak economy at a time when the government’s consumer protections were being curtailed. The Reagan administration, Ms. Karpatkin told The New York Times in 1982, had “eviscerated the Consumer Protection Agency.”

“And the Federal Trade Commission,” she added, “now takes the view that consumers are willing to risk their dollars in the marketplace and buy products that are shoddy and falsely advertised. I think there will be a field day for fraudulent advertising and for shoddy products.”

Rhoda Alayne Hendrick was born on June 7, 1930, in Brooklyn to Charles and Augusta (Arkin) Hendrick, immigrants from Eastern Europe. Her mother was a homemaker, her father a salesman.

After graduating from Lafayette High School, she enrolled in Brooklyn College, where she edited the The Vanguard, a student newspaper, and was denounced by the Student Council president as left-wing. After earning a bachelor’s degree in 1951, she decided to pursue law instead of journalism.

She wanted “to do important things, not report on them,” she told The Times in 2000.

In 1951, she married Marvin M. Karpatkin; he died in 1975. In addition to their daughter, she is survived by two sons, Herb and Jeremy Karpatkin; 10 grandchildren; and four great-grandchildren. Her partner, Bruno Aron, died in 2009.

Ms. Karpatkin graduated from Yale Law School in 1953 and practiced from 1954 through 1974, specializing in consumer and education law. She represented conscientious objectors and handled civil liberties cases. As chairwoman of an Upper West Side community school board in Manhattan, she was active in the school decentralization movement.

As executive director of Consumers Union, Ms. Karpatkin hewed to her early commitments to labor, civil and women’s rights. She championed a single-payer health care system, under which medical care is provided and paid for by one public authority.

As president of the International Organization of Consumers Unions (which was renamed Consumers International), she monitored the policies of multinational corporations, the impact of globalization and trade agreements. During her travels to Africa, Latin America and Asia, she urged governments and business executives to make health care and adequate food supplies a fundamental human right.

She retired in 2001.

As a young woman, Ms. Karpatkin told The Times, she regarded Consumers Union as “as one of the quintessential do-good organizations.”

“You just got the feeling they couldn’t be bought, couldn’t be seduced,” she said.