Drug testing is increasingly used in the screening of applicants for employment. Despite the growth of drug testing, there is little research that examines the value of pre-employment drug-use information in the prediction of post-employment suitability. This research, which was based on a sample of 10,188 young adults, examined the criterion-related validity of pre-employment drug-use information. For all drugs examined, the greater the frequency of use and the earlier the age at which the drug was first used, the greater the probability of a person being classified as unsuitable after hire. However, the operational validity of each drug variable was influenced by the base rate of drug use. The low base rates for some drugs make their operational validity of limited value. The operational validity of the marijuana frequency-of-use measure (.07) was approximately equal to that of less frequently used drugs (e.g., stimulants and depressants). No strong moderators of the validity of a drug-composite measure were found.