The operative mortality for biliary tract obstruction due to malignancy is high. In 1981 a controlled clinical trial of pre-operative percutaneous drainage was started at the Royal Postgraduate Medical School. At the time of percutaneous transhepatic cholangiography patients were randomized either to laparotomy or to pre-operative percutaneous transhepatic biliary drainage ( PTBD ) followed by laparotomy. Only patients with malignant biliary tract obstruction and serum bilirubin greater than 100 mumol/l were included. Seventy patients entered the trial, and five were withdrawn. Of the 65 remaining, 31 underwent laparotomy and 34 had pre-operative PTBD followed by laparotomy. The median duration of drainage was 18 days and during this time the median bilirubin fell from 305 to 115 mumol/l. Five patients required early surgery for complications of PTBD and two died within 30 days of surgery. The mortality for laparotomy was 19 per cent (6/31) compared with 32 per cent (11/34) for drainage plus laparotomy. This trial highlights the hazards of PTBD in high risk patients and has failed to demonstrate a reduction in mortality with the use of pre-operative PTBD .