AbstractA consecutive 10‐year series of 278 soft tissue sarcomas was prospectively graded, using a system based on the number of mitoses and taking into account parameters such as cellularity, anaplasia, necrosis, and histogenetic type and subtype of tumour. Prognostic factors in relation to metastasis‐free survival were studied by uni‐ and multivariate analysis.Fifty‐seven (20·5 per cent) were low‐grade tumours, 43 (15·5 per cent) were intermediate, and 178 (64 per cent) were high grade. High‐grade tumours were divided into two groups; 80 (29 per cent) grade 3A (=5–20 mitoses per 10 high power fields (HPF)) and 78 grade 3B (28 per cent) (=more than 20 mitoses/10 HPF); 10 HPF corresponds to 2·5 mm2. Twenty (7·2 per cent) high‐grade tumours could not be further subdivided.Grading was found to be the prognostic factor associated with the strongest predictive value. Five‐year survival in low‐grade and intermediate tumours (95 and 86 per cent, respectively) differed significantly (P<0·0001) from high grade (50 per cent) and (P= 0·0018) between grade 3A (64 per cent) and grade 3B (41 per cent). Other prognostic indicators of importance in high‐grade tumours were age, local recurrence at presentation (primary operation outside the Centre), and localiza