The relative costs were analysed of (1) no prophylaxis against deep vein thrombosis (DVT), (2) selective treatment of DVT after confirmation of diagnosis, (3) general prophylaxis with standard low-dose unfractionated heparin and (4) general prophylaxis with low molecular weight heparin (LMWH) in patients undergoing elective general abdominal surgery or elective hip surgery. The mean calculated costs per patient undergoing general abdominal surgery were: Swedish crowns (SEK) 1950 for no prophylaxis, SEK 5710 for selective treatment of DVT, SEK 735 for prophylaxis with unfractionated heparin and SEK 665 for prophylaxis with LMWH. The corresponding costs for hip surgery were SEK 3930, SEK 10 790, SEK 1730 and SEK 1390 respectively. Thus, the least expensive management strategy in patients undergoing elective general abdominal or hip surgery would appear to be general prophylaxis with either unfractionated heparin or LMWH. Furthermore, general prophylaxis with LMWH would appear to be more cost-effective than general prophylaxis with unfractionated heparin.