BACKGROUND: An increasing number of antidepressants have been released on the United Kingdom market in recent years, and these are being prescribed more frequently in general practice. Clinical trials suggest that such agents have similar efficacy and the choice of drug is probably based on tolerability, toxicity in overdose, and cost. AIM: To compare the tolerability and safety profile of six, newly marketed antidepressants used in general practice. METHOD: Studies have been conducted for six antidepressants: fluoxetine, sertraline, paroxetine, moclobemide, venlafaxine, and nefazodone, using the technique of prescription-event monitoring. Patients were identified using incident dispensed prescription data. Questionnaires were sent to patients' general practitioners six months after the date of first prescription. Questionnaires asked for date of birth, sex, indication for prescribing each drug, and all events entered in the patients' records after the date of first prescription. RESULTS: Each cohort exceeded 10,000 patients. Nausea/vomiting was the most frequently reported event for all drugs. The difference in incidence rates for drowsiness/sedation, male sexual dysfunction, and hypertension is shown. Mortality data are also reported. CONCLUSION: Frequently reported events were similar for all six drugs but there were clinically and statistically significant differences for less frequently reported events. The adjusted mortality rate was identical between the six drugs. This study provides valuable comparative data for six, widely used antidepressants in general practice.