Two approaches were used to estimate the amount of illicit drugs consumed and available for consumption in the United States. Estimates of the number of drug users were multiplied by estimates of the average amount of drugs consumed. Then the supply of drugs available for consumption was examined by estimating the amount of drugs that enters the United States and escapes seizure. Prevailing retail prices were used to convert drug amounts to dollar value when sold to final users. The results indicated Americans spent approximately $18 billion on cocaine, $12 billion on heroin, $9 billion on marijuana, and $2 billion on other illegal drugs in 1990. Retail sales of both cocaine and marijuana appeared to have fallen by about 24% from 1988 to 1990, while retail sales of heroin seem to have fallen slightly less, by about 22%. Approximately 263-443 metric tons of cocaine were available for domestic consumption. The net effect of increases in both production and foreign and all seizures has been a 22% decrease in the amount of cocaine available for consumption in the United States between 1988 and 1990. Estimates are reliable enough to imply that the trade in illicit substances is immense, roughly $40 billion to $50 billion. The social costs from drug consumption greatly exceed the amount spent on illicit drugs themselves. (ABL)