The cost of drugs to users can provide a number of valuable insights to researchers, such as the size of drug markets, drug-related criminal activities, and challenges for treatment. Until recently, most estimates of drug costs have relied on holistic reports of how much respondents spent on drugs. However, in 2000 the ADAM program questionnaire contained highly specific questions regarding drug costs. The current study examined ADAM data from a sample of 2,979 Manhattan arrestees during 2000-02 and compared it with ADAM data from 1998-99 regarding drug costs. Covariance of drug expenses were analyzed, revealing that among the 2000-02 Manhattan arrestees who reported obtaining drugs in the past 30 days, the median drug expense was estimated at $370 per month. Frequency of use accounted for 42 percent of the variance. Infrequent marijuana-only users had the lowest monthly drug expense at $5 per month, while heavy marijuana-only users spent an estimated $600 per month. Heroin and cocaine costs to Manhattan arrestees were estimated at $1,000 or more per month. When compared to the 1998-99 estimates, the drug costs for 2000-02 were twice as large. While it appears that ADAM’s more specific questions regarding drug costs may advance the estimation of drug expenses, more research is necessary to conclusively establish the accuracy of the estimator. References, tables, figures