Background and study aims: Endoscopically placed metallic biliary stents provide durable drainage for malignant biliary obstruction. The best-studied metal stent is the Wallstent, which has a greater duration of patency than polyethylene stents. Recently, the Ultraflex Diamond stent has been introduced, with reports from Europe which suggest efficacy similar to that of the Wallstent. We report our experience with this new metal stent and compare it with a historical cohort of Wallstent-treated patients. Patients and methods: Between July 1997 and July 1998 all metal stents placed for malignant biliary obstruction were Diamond stents (10 mm diameter, 6 or 8 cm length). Prospective follow-up details with regard to patient death or stent occlusion were obtained. In total, 32 patients underwent stenting, but 11 patients were excluded because of the following: death from pre-existing cholangitis (2); placement of bilateral hilar stents (2); placement of stent through occluded metal stents (3); failure to palliate jaundice due to complex hilar stricture (2) or concomitant liver failure (1); or inability to obtain follow-up (1), leaving 21 patients for analysis. Occlusion rates and stent patency were also determined retrospectively for 19 patients with malignant biliary obstruction who had Wallstents (10 mm diameter, 6.8 cm length) placed during the preceding year and for whom accurate and complete follow-up details were available. Results: In the Diamond stent group there were 14 men and seven women, mean age 73. In the Wallstent group there were 11 men and eight women, mean age 66. The types of cancer, level of stricture and percentage with prior polyethylene stenting were similar in both groups. Stent occlusion occurred in 9/21 (43%), Diamond stents at a mean of 74 ± 43 days compared with 8/19 (42%) Wallstents at a mean of 178 ± 138 days (P < 0.04). Mean time of stent patency was 110 ± 89 days for Diamond stents and 253 ± 218 days for Wallstents (P < 0.01). Analysis of occlusion-free survival using a Kaplan-Meier plot showed a trend favoring the Wallstent (P = 0.12; Wilcoxon test). Conclusions: The occlusion rate and patency of Diamond stents for malignant biliary obstruction appear to be inferior to those of Wallstents and similar to reported values for polyethylene stents. Prospective randomized comparisons of Wallstents and newer self-expanding metal stents are warranted.