We report two fatalities that are related to the cathinone 4-methylethcathinone (4-MEC) and review the current knowledge of 4-MEC. Qualitative and quantitative analysis of 4-MEC was performed by validated high performance liquid chromatography-tandem mass spectrometry methods. In the first case a 22-year-old male died in hospital following collapse and seizures after using 4-MEC. Toxicological analysis of postmortem femoral blood revealed the presence of 4-MEC (0.167 mg/L), ethanol (27 mg/100 mL) and paracetamol (5 mg/L). Death was attributed solely to 4-MEC toxicity. The second case involved a 54-year-old man found with a taped plastic bag over his head. Toxicological analysis of postmortem femoral blood revealed the presence of 4-MEC (1.73 mg/L) along with ethanol (229 mg/100 mL), propranolol (0.036 mg/L), venlafaxine (0.284 mg/L) and its metabolite O-desmethylvenlafaxine (0.205 mg/L), and diazepam (<0.005 mg/L) and its metabolite nordiazepam (0.033 mg/L). Death was attributed primarily to asphyxiation. These cases and a review of the current knowledge of 4-MEC pharmacology/toxicology adds to the body of case material for 4-MEC and will assist with interpretation in postmortem toxicology cases in which 4-MEC is detected.