ObjectiveTo characterize time trends in incidence of intraepithelial and invasive vulvar neoplasia, transition of intraepithelial vulvar neoplasia to invasive cancer, and survival rate based on a total population.MethodsThe Cancer Registry of Norway was used to identify all Norwegian inhabitants diagnosed during 1956-1990 with squamous cell carcinoma of the vulva, and all those with intraepithelial vulvar neoplasia diagnosed during 1973-92.ResultsThe incidence rate of intraepithelial neoplasia increased three-fold from 1973-77 to 1988-92, and 3.4% changed into invasive disease. Multivariate analyses identified age as a significant variable. The age-adjusted incidence rate for squamous cell carcinoma was constant for the whole period. The ratio between recurrence and the total number of invasive cancer varied from 21% to 31%. The 5-year survival rates have not changed significantly over the period. Age was revealed as a strong prognostic factor, showing an excess death rate by increasing age.ConclusionThe incidence of vulvar intraepithelial neoplasia has increased substantially over the last 40 years, but that of invasive vulvar cancer has not changed appreciably.