Duquenois–Levine reagent

The Duquenois reagent used in the Rapid Modified Duquenois–Levine test (also known as the simple Rapid Duquenois Test), is an established screening test for the presence of cannabis. The test was initially developed in the 1930s by the French Medical Biochemist, Pierre Duquénois (1904–1986), and was adopted in the 1950s by the United Nations as the preferred test for cannabis, and originally claimed to be specific to cannabis.

After several modifications, it became known as the Duquenois–Levine test. However, in the 1960s and 70s various studies showed that the test was not specific to cannabis. In 1973, the Supreme Court of Wisconsin ruled the D–L test insufficient evidence for demonstrating that a substance was cannabis, specifically noting that the D–L tests used "are not exclusive or specific for marijuana."

The test is one of several forms of modern cannabis drug testing.