SAN FRANCISCO—The number of major U.S. companies covering the cost of gender reassignment surgery for transgender workers has more than doubled in the past year, according to a new scorecard compiled by the nation's largest gay rights group.

The Human Rights Campaign said in a report to be published Thursday that 207 of the 636 businesses it surveyed for its annual Corporate Equality Index either are already providing transgender- inclusive employee health benefits or plan to at the start of the new year.

Last year, 85 companies had insurance plans that paid for sex transformation surgeries, and only 49 did in 2009. A decade ago, when the campaign launched the index, none did.

The major force behind the jump is the fact that this is the first year the Human Rights Campaign graded corporations and law firms on whether their medical plans paid for the full complement of procedures workers might need to transition to a new gender on the job, from psychological counseling to genital reconstruction.

To maintain a coveted 100 percent and a listing in the campaign's preferred vendors' guide for gay, lesbian and transgender consumers, companies had to offer at least one insurance plan that covers at least $75,000 worth of surgery and other treatments recommended by a patient's doctor.

"We really wanted to set a best-in-class standard for what it meant to provide the holistic class of LGBT inclusion in the workplace," campaign spokesman Fred Sainz said.

Among the corporations that expanded their insurance coverage this year are Apple, Chevron , General Mills , Dow Chemical , American Airlines, Kellogg, Sprint, Levi Strauss, Eli Lilly , Best Buy , Nordstrom , the U.S. division of Volkswagen , Whirlpool , Xerox , Raytheon and Office Depot .

Frantz Tiffeau, senior manager of supply chain diversity at Florida-based Office Depot, said the decision to cover transgender surgery was made by senior executives who understood the procedures to be medically indicated, not elective. The office supplies company already had had employees change genders, before the new health plan was adopted.

"Realistically, we just looked at it as a necessity," Tiffeau said. "Our executive V.P. said, `It's the right thing to do, it's something we support and we have employees who have this need."

To bolster its ranking on the campaign's index, Office Depot also has started sponsoring gay rights events such as an annual leadership conference held by the National Gay and Lesbian Task Force. The activities have not produced negative reactions from customers, Tiffeau said.