Two patients presented with severe side effects of theophylline. Due to the theophylline intoxication patient A developed ischaemic hepatitis, which made haemodialysis treatment necessary to accelerate the elimination of the drug from the body. The intoxication caused immobilisation and total dependence with respect to the daily activities of patient B. In neither case was the association between mood disorders--like depression, agitation and anxiety--and an overdose of theophylline recognised. Administration of theophylline should be monitored with regular measurements of the serum theophylline concentration, because of its narrow therapeutic margin and the serious toxic side effects.