The activities of 90Sr in the surface waters of the Adriatic Sea were investigated twice a year over the period 1963 – 1990 at four locations. A tendency was noted for the maximum concentrations to occur in the first half of the year. This can be explained by reflection of common spring activity peak on surrounding land masses. The 90Sr activity of the North Adriatic region was greater than the activities of south regions in both spring and autumn. The main residence time of 90Sr in the mixed sea-water layer was practically identical at all locations. The lower limit of 90Sr sedimentation rate in the Adriatic Sea was estimated to be 2.4 x 10-8 m s-1, the upper limit being 4.9 x 10-7 m s-1. The Chernobyl nuclear accident did not affect the activity of 90Sr in the Adriatic surface waters
