Summary. This paper presents the chemical composition of the main sulphur springs in Croatia and compares it with the sulphur content in the water from the Split spa. It also presents the results of monitoring the content of chlorides and hydro- gen sulphide as well as the sulphur water temperature during 1987, 1988 and 1996 with the objective of studying the hydro- logical characteristics of this water and its origin. Since the sulphur water content during the dry periods significantly differs from the sulphur water content during rainy winter periods, this paper also compares the results obtained for the mentioned two periods. According to the monitoring results it can be concluded that sulphur water consists of seawater, and hydrocarbonate surface water with a fairly constant water content during dry periods, while the hydrocarbonate water con- tent increases during rainy periods.