In a six-month double-blind study in an inpatient chemical dependency facility, 29 cocaine-dependent subjects were studied to determine if the amino acids, L-tryptophan and L-tyrosine, would decrease cocaine craving and withdrawal symptoms. Those subjects receiving placebo were shown to have a statistically significant increase in only one physical symptom category. The drug craving and other major physical and subjective symptoms were not shown to be significant. This study is consistent with a literature review in demonstrating that the amino acids do not significantly reduce most symptoms of cocaine craving and withdrawal when used alone.