From January 1987 to December 1987, 193 radial artery cannulations were performed in 112 patients (87 males, 25 females; mean age = 57.5 years). The mean duration of cannulation was 6.45 days. After removal, the tip of the catheter was cultured using a semiquantitative culture technique: 164 catheters were cultured and positive results were seen in 37 cases (22.5%); 98 samples of infusate were cultured. Positive results were observed in 23 cases (23.5%). No bacteriological correlation was found between these two culture results. During the study, no catheter-related or infusate-related bacteraemia was detected. It is concluded that nosocomial infections associated with long-term radial artery cannulation are not commonly seen, in particular no catheter or infusate-related bacteraemia occurs even if the duration exceeds 4 days.