The purpose of this study was to examine the relationship between antemortem (AM) and postmortem (PM) morphine and codeine concentrations in whole blood. In addition, the effects of antemortem to death interval as well as the postmortem interval were considered during the interpretive process. The cases of seven human subjects are presented here with an average postmortem interval of 28 h (13.5-48 h) and an average antemortem to death interval of 97 min (ranging from 9 to 300 min). Drug concentrations were obtained from AM blood collected from local hospitals in Miami, FL, and postmortem blood was obtained from the Miami-Dade County Medical Examiner Department in Miami, FL. The results obtained for this study indicated that factors such as metabolism and postmortem interval can affect postmortem drug concentrations in an unpredictable manner. Four out of seven morphine cases appeared to be affected by postmortem redistribution, and five of seven codeine and two of two 6-monoacetylmorphine cases were affected as well.