This study of 30 cats with mammary carcinoma was designed to investigate the relationship between (1) six nuclear morphometric parameters (mean nuclear profile area [MNA], standard deviation of MNA [SDa], coefficient of variation of MNA [CVa], nuclear form factor (p2/4 pi area) [FF], standard deviation of FF [SDf], and coefficient of variation of FF [CVf]) assessed by image analysis, and (2) survival for > 1 year or < 1 year after surgical removal of the tumour. Only the SDf and the CVf appeared to be related to survival. Cats that died within 1 year had an SDf or CVf (or both) higher than the corresponding mean values (SDft and CVft) for all 30 cats; but only four of 16 cases (25%) with a SDf lower than SDft and five of 17 cases (29.4%) with a CVf lower than CVft died within 1 year. The authors conclude that SDf and CVf represent reliable prognostic parameters in feline mammary carcinomas.