. In the framework of the Interreg II Project (July 1998 ‐ June 2001), hydro‐logical, chemical and biological data were collected in the Gulf of Trieste. During spring and summer 2000, some particular thermohaline anomalies were observed in the Gulf of Trieste. Especially in May and June the water body showed: a very strong thermohaline stratification, an increase of advective salt water coming from the south and the presence of sharp pycnoclines. In July the temperature was higher than usual in the whole water column. Moreover, in late May and in June, massive mucilaginous aggregates were observed along the water column and at the surface. In order to highlight these particular thermohaline features the hydrological data of 16 stations were analysed (Fig. 1). Two stations, in particular, were considered: one offshore (St. AA1, average depth 20 m) and one close to the coast (St. C1, average depth 17 m). For these two stations a best‐fit analysis, computed over 11 and 7 years, respectively, was performed on temperature, salinity and density excess data. Moreover, the hydrological features were compared with the rainfall, air temperature, wind speed data (Istituto Sperimentale Talassografico di Trieste ‐ ISTT) and the Isonzo River's flow rate (Direzione Regionale dell'Ambiente ‐ Regione F. V. G.) collected from January 1998 to December 2000.