Studies examining post-mortem processes are difficult to conduct since changes will have already occurred when the body arrives at the mortuary. While control of collection site for blood can minimize changes in concentration it is very difficult to conduct experiments in humans aimed at understanding the mechanisms and determining the extent of such changes. The use of appropriate animal models can be useful in this regard providing the species and conditions are carefully chosen. Pharmacokinetic studies in humans are also very useful for understanding the changes in drug concentration with time in blood (and other fluids) and also for improving our understanding of drug effects. Unfortunately, doses of illicit drugs that can be given are relatively low to guarantee safety hence extrapolations are made to real life situations. Individual case studies can be useful to describe an unusual or particularly interesting circumstances but little useful information can be obtained when trying to ascertain the role of competing factors, e.g. role of individual drugs when multiple drugs are present, varying toxicity between route of administration, and the role of age or natural disease when drugs are also present. Epidemiological approaches by reviewing large numbers of related cases are the most powerful tool to obtain this information. All of these studies need to operate under the ethical and legal framework appropriate for a jurisdiction. This paper discusses the relative merits of scientific approaches to research in post-mortem toxicology and provides guidance on the most appropriate techniques for future studies.