An elevation of serum aspartate aminotransferase (GOT) and alanine aminotransferase (GPT) may be produced in patients treated with i.v. full-dose HEPARIN. We studied the influence of low-dose s.c. HEPARIN (5,000 IU X 2) in 34 patients with acute myocardial infarction (AMI) and in 7 with cerebrovascular accidents or calf thrombophlebitis. Twelve patients (all males) with AMI showed a secondary elevation of GOT and GPT at about the sixth or seventh day after the commencement of therapy that persisted throughout the period of treatment. Four patients (two males and two females) with cerebrovascular accidents or thrombophlebitis showed similar increases of GOT and GPT.