Covance was founded in 1968 as Environmental Sciences Corporation in Seattle, Washington.
In 1972 the company bought Hazleton Laboratories, a laboratory that conducted toxicology testing, and took on that name. By 1982, Hazleton had become the largest biological testing company in the U.S.
Covance was purchased by Labcorp in 2014 in a $6.1 billion deal.
Today the company provides testing services, including toxicology studies and biostatistical analysis for pharmaceutical and biotech companies. Other clients include companies in the food, agrochemical, and chemical industries. The company also provides testing services which include designing and realizing human clinical trials.