The biological behaviour of acinic cell carcinomas, even if well differentiated, is unpredictable. We studied 45 patients with acinic cell carcinoma followed-up from 10 to 379 months (5 year recurrence-free and survival rate of 69% and 81% respectively), and compared clinico-pathological parameters with outcome. The presence of a predominately solid architecture was strongly associated with a poor outcome (P < 0.01) and this was the only independent prognostic variable when log rank testing was performed. Tumour size (> 2.75 cm) was a significant predictor of recurrent deep parotid lobe involvement, the presence of cervical nodal disease and lymphocytic infiltration, although not significant, factors showed a tendency towards recurrence. For acinic cell carcinoma, the predominant solid architecture would appear to be a strong predictor of recurrence.