Non-specific abdominal complaints are a very frequent cause of discomfort. Even if only comparatively few are brought to the attention of the physician, they account for a considerable portion of the reasons for seeking medical care, both in acute and chronic conditions. On the other hand, few drugs are free of the suspicion of causing abdominal complaints, which make up between one-tenth and one-third of reported adverse reactions. A wide variety of possible alternative or concomitant causes makes a clear causative attribution to suspected drugs very difficult. This holds especially true for the ill-defined conditions of indigestion and anorexia. For nausea and vomiting, specific scales have been developed which facilitate differentiation between drugs causing these effects most frequently and most intensively. They have been applied in cytostatic therapy, where this is one of the most frequently encountered problems, but nausea and vomiting can seriously affect compliance in many other treatments. Somatic abdominal pain results in most instances from the irritation of the parietal peritoneum and is usually the effect of a lesion. This may or may not be caused by a drug, but this cause should be the first consideration. Visceral pain may result from functional disturbance of secretory glands or of the muscular coat, from drug action on bowel content or from irritation of the mucosa, all of which are frequently interrelated. Most frequently suspected pharmacological causes are drugs with anticholinergic action, antibiotics, potassium supplements and non-steroidal, anti-inflammatory agents. Drug-induced hyperinsulinism and porphyria are rare cases. Abuse of laxatives should always be considered because of its prevalence. A great number of other untoward drug effects have been described in the literature, but rarely merit first consideration. With the exception of promptly occurring or persistent emesis, gastrointestinal symptoms usually are not pathognomonic for drug effects and are the result of several factors. The usual approach to identifying an adverse drug effect is to delineate the functional or structural disorder, and to associate this diagnosis with possible pharmacodynamic aetiologies.