This study has shown that extent of resection was the most important variable involved in the development of anaemia and B12 deficiency in patients matched in pairs for all other factors thought to affect haemoglobin and serum-B,, levels, following gastrectomy. Differences in incidence of anaemia and of subnormal serum-B,, levels related to ulcer site or gastrectomy type were comparatively small. Explanations are offered of how substantial variations in extent of resection occur and give rise to differences in haemoglobin and serum-B,, levels which may appear to be related to ulcer site and operation type. Serum-folate levels were also often low after moderate gastrectomy and were lower still after more radical resection. However, in the small numbers considered the difference was not statistically significant.