A gas chromatography-ion trap-tandem mass spectrometry method was developed and validated for the simultaneous solid-phase extraction and quantification of cocaine, benzoylecgonine, cocaethylene, morphine, codeine, and 6-monoacteylmorphine in blood, muscle tissue, and water. An assay for total morphine in blood and muscle was also validated. The limit of quantification was ≤ 0.01 mg/kg in muscle and ≤ 0.005 mg/L in blood and water. Good linearity was observed over the concentration ranges studied (r ≥ 0.99). The repeatability (% RSD) at the three concentration levels was typically ≤ 15% and never exceeded 17%. Intermediate precision of ≤ 16% was obtained for all matrices. Deviation < 20% of the nominal concentration was obtained in all repeatability and intermediate precision experiments. Extraction recoveries for cocaine and metabolites ranged from 91% to 110% in water, 81% to 110% in blood, and 61% to 75% in muscle. Recoveries for opiates ranged from 59% to 104% in water, 50% to 95% in blood, and 41% to 79% in muscle. The hydrolysis efficiency for the total morphine assay in blood and muscle ranged from 91% to 99% with within-day and intermediate precisions of ≤ 14% and ≤ 12%, respectively.