A 3-year prospective study of the learning curve for D2 gastrectomy was carried out by one surgeon beginning to perform the operation independently after intensive specialist training. Some 38 patients were treated; there were four postoperative deaths and 22 patients had complications. Postoperative morbidity decreased significantly with time (rS = -0.38, P = 0.02, 95 per cent confidence interval -0.62 to -0.07). The physiological component of POSSUM (Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity) was significantly lower in the third year (median value 15, 16 and 14 for years 1, 2 and 3, n = 31, chi 2 = 7.5, 2 d.f., P = 0.02, Kruskal-Wallis test), but the operative POSSUM scores and the number of lymph nodes found were not decreased (median operative POSSUM score 19, 18 and 21, n = 31, chi 2 = 0.2, 2 d.f., P = 0.91, Kruskal-Wallis test). The results suggest a learning curve lasting about 18-24 months or 15 to 25 procedures before a plateau is reached. Improved results were associated with changes in case selection and operative tactics but not with reduced extent of lymphadenectomy. D2 gastrectomy should be restricted to specialist centres where adequate training and supervision can be provided during the learning curve.