This paper presents the results of two year's of research of the coastal seawater and sandy sediments along the beach in Sopot. The investigations were performed from May 1997 to April 1999. Four testing sites, perpendicular to the shore, were chosen in the area located between the mouths of two streams, Grodowy Potok and Kamienny Potok. It was revealed that the total number of mesophilic bacteria increased as distance from the waterline increased. In contrast, the number of E.coli was highest in the coastal water and in sand points close to the water. This indicates that there are two sources of microbiological pollution at work on sandy beaches. The first source is seawater which contains E. coli bacteria and the second is polluted air from the land that conveys the mesophilic bacteria, The high levels of E. coli bacterial pollution in the sand in the spring-summer season indicate that it is essential to monitor the sanitary conditions of this area during this period.