Positivity Rates by Drug Category for The General U.S. Work Force
(as a percentage of all positives)

DRUG CATEGORY 2001 2000 1999 Acid/Base 0.23% 0.07% 0.14% Amphetamines 5.50% 4.80% 4.30% Barbiturates 3.20% 3.50% 3.70% Benzodiazepines 5.00% 4.20% 3.30% Cocaine 13.20% 13.90% 15.80% Marijuana 60.90% 63.0% 62.60% Methadone 0.98% 0.89% 0.45% Methaqualone 0.00% 0.00% 0.00% Opiates 5.50% 5.20% 5.10% Oxidizing Adulterants (incl. Nitrites) 0.51% 0.88% 1.60% PCP 0.46% 0.45% 0.35% Propoxyphene 4.00% 2.50% 2.00% Substituted 0.48% 0.56% 0.80%

Source:

Quest Diagnostics: Drug Testing Index (Online)