The subjects were 36 black male chronic crack cocaine users unmotivated in drug abuse treatment, willing to be studied for daily payment, who were recruited by word of mouth on the street. Of the 464 CPK results obtained, the mean CPK value was 397 (SD=784)IU/L. Two-thirds of the results were greater than 200; 19 percent were greater than 500 IU/L. CPK test results were systematically eliminated if related to medical causes or concurrent other drug use. The relative contribution of recent alcohol use versus recent cocaine use in raising CPK was assessed by dividing the remaining 435 observations into sequential use groups. With alcohol-use instances excluded, a statistically significant relationship between urine cocaine metabolite and elevated CPK was found. When all other possible causes of elevated CPK levels were controlled, crack cocaine use was associated with a significant quantitative effect on CPK level. 1 table and 45 references