99Tcm-pyridoxylidene glutamate (99Tcm-PG) scans have been carried out in 24 jaundiced adults (mean total bilirubin 255 mumol/l and 11 infants with prolonged obstructive jaundice (mean total bilirubin 165 mumol/l). Absence of radioactivity in the gut was interpreted as complete biliary obstruction which was the cause of jaundice in ten adults and six infants. Using this criterion occlusion or patency of the bile ducts was correctly determined in 21 adults and eight infants. False-negative gut images were found in one adult and two infants, and three scans were inconclusive (two adults, one infant). The scan was unable to show details of the site of obstruction or pathology but the technique was simple and atraumatic and was safely performed in patients with serious complications, e.g. renal failure, coagulation defects, septicaemia. In infants the 99Tcm-PG scan compared well with the 131I rose bengal faecal excretion test and with liver biopsy in the investigation of prolonged obstructive jaundice. Repeat scans in infants with biliary atresia were used to assess postoperative bile drainage. It is suggested that 99Tcm-PG scanning is useful screening test in difficult cases of jaundice. It is especially useful in frail patients, and patients with complications.