The survey, published in the December/January edition of Worth magazine, counted both gifts of cash and in-kind goods and services.
Merck gave $148.5 million to charity last year, including the value of drug donations, such as the river-lindness drug Mectizan.
DuPont contributed $122.2 million in programs for community development, education and the environment.
Tobacco company Philip Morris gave $98 million, the largest cash donation, to support hunger relief and the arts.
Intel Corp., which was 12th on the list, donated $70 million, including funds for a program to train 400,000 teachers in 20 countries to use computers in classroom teaching.
Pharmaceutical makers have faced pressure as of late to donate medicine to poor countries to help them battle treatable diseases.
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