Four deaths related to the drug 4-methylmethcathinone (mephedrone) are reported. Qualitative and quantitative analysis of mephedrone was performed by high-performance liquid chromatography-diode-array detection. Of the four deaths, one was attributed to the adverse effects of mephedrone, with cardiac fibrosis and atherosclerotic coronary artery disease as a contributing factor. A 49-year-old female insufflated mephedrone; analysis disclosed mephedrone in femoral venous blood (0.98 mg/L). The second death was attributed solely to mephedrone. A 19-year-old male took mephedrone as well as alcohol and "ecstasy" ; analysis disclosed mephedrone (2.24 mg/L femoral venous blood) and 3-trifluoromethylphenylpiperazine (3-TFMPP). In the third fatality, a 55-year-old female was found dead in bed; the death was attributed to the combined effects of mephedrone and methadone. Analysis of femoral venous blood revealed the prescribed drugs diazepam, nordiazepam, olazepine, and chlorpromazine metabolites together with methadone (0.3 mg/L) and mephedrone (0.13 mg/L). In the fourth case, a 17-year-old male car driver was involved in a vehicular collision and died of multiple blunt force injuries. Analysis revealed mephedrone in femoral venous blood (0.24 mg/L).