While there are many systems available for postmarketing surveillance today, none is ideal for every situation. Recent progress has been made through computerised data bases which allows for rapid identification of patients with diseases or drugs of interest. Careful planning, with attention to the relative strengths and weaknesses of each, will permit the investigator to choose the optimum system to answer the postmarketing surveillance problem. While postmarketing surveillance cannot prevent adverse drug reactions, it can increase the safety of drug use and detect adverse reactions early, thereby limiting the cost to our population.