The effect of chlorpromazine (CPZ) on the larval length and width of Sarcophaga haemorrhoidalis (Fallén) (Diptera: Sarcophagidae) was investigated under laboratory conditions for possible implications for forensic investigations. Fresh beef was treated with one of four concentrations of CPZ (0, 0.5, 1.0, and 1.5 μg per g of beef) to simulate postmortem concentrations in CPZ-dosed corpses. Ten replicates of 50 S. haemorrhoidalis eggs each were placed on the treated beef and maintained at 27°C. The length and width of 2 d old and 4 d old larvae were measured for all treatments and replicates, and the presence of CPZ in the treated meats was qualitatively verified using liquid chromatography–mass spectrophotometry coupled with electrospray ionization. Pearson's product-moment correlation coefficient revealed significant correlations of CPZ concentration with both larval length and width at the two larval ages (P < 0.001). However, the mean length and width of larvae fed on CPZ-treated beef did not differ significantly from the length and width of larvae fed on untreated control meat, except with larvae fed on 1.5 μg CPZ per g meat (P < 0.001). We conclude from these laboratory assays that S. haemorrhoidalis larvae may prove to be a reliable model to use in the estimation of the minimum postmortem interval in corpses that contain CPZ <1.5 μg/g.