The company performed more than 7.1 million drug tests from January to December 2003, including 5.9 million tests among the general workforce. Among the general workforce (which excludes tests given to federally mandated, safety sensitive workers), 5 percent of all tests performed by the company came back positive in 2003, compared with 4.8 percent in 2002.

The company's drug-test data suggest that greater use of methamphetamine, a type of amphetamine, among a large group of general U.S. workforce employees during 2003 helped drive the increase. For this group of workers, the incidence of positive drug tests attributed to methamphetamine increased by more than 68 percent from 2002 to 2003, reaching 0.32 percent of all positive drug tests, which is up from 0.19 percent in 2002.

The study also found that the incidence of positive drug tests attributed to opiates grew by more than 25 percent from 2002 among general U.S. workforce employees. Marijuana remains the drug most frequently found in workplace drug tests.