The aim was to describe the regional variation of population based surgery rates in Finland with special reference to the comparison of surgical activities in individual hospitals. Data on 11 common procedures covering all Finnish hospitals were obtained from the Finnish Hospital Discharge Register and the Finnish Medical Birth Register of the years 1987 and 1988. The variations of age and sex standardized procedure rates were studied across the procedure specific hospital service areas. The variation was estimated by three methods: extremal quotient, coefficient of variation, and systematic component of variation. The statistical significance of the variation measures was tested with a computerized simulation model. The variation was small for mastectomy, inguinal hernia repair, and hip replacement due to fracture, and large for lumbar disc operations, haemorrhoidectomies, and uterus operations. The results are similar to those of comparable studies elsewhere. The results indicate that there are clear differences in surgical activities between Finnish hospitals.