The larvae of necrophagous fly species are used as forensic tools for the determination of the minimum postmortem interval (PMI). However, any ingested drugs in corpses may affect larval development, thus leading to incorrect estimates of the period of infestation. This study investigated the effects of methamphetamine and its metabolite, p-hydroxymethamphetamine, on the forensically important Australian blowfly Calliphora stygia. It was found that the presence of the drugs significantly accelerated larval growth and increased the size of all life stages. Furthermore, drug-exposed samples remained as pupae for up to 78 h longer than controls. These findings suggest that estimates of the minimum PMI of methamphetamine-dosed corpses could be incorrect if the altered growth of C. stygia is not considered. Different temperatures, drug concentrations and substrate types are also likely to affect the development of this blowfly. Pending further research, the application of C. stygia to the entomological analysis of methamphetamine-related fatalities should be appropriately qualified.