Between 1989 and 2003 colonies of Little Terns (Sterna albifrons) occurring in the lagoon of Venice (55,000 ha; Italy) have been surveyed. Each year the number of breeding pairs ranged between 31 (in 1997) and 611 (in 1995), with a yearly mean of 205 (SD = ±163). An overall stability in breeding numbers was observed, with an increase from 1989 to 1995 and a decrease afterwards. 34 sites were used; 13 (38%) were saltmarsh islets, twelve (35%) dredge islands, four (12%) beaches and the remaining five (15%) artificial beaches. Colony size median ranged between 25 and 15 pairs, with no differences among site typology. Sites used each year ranged between one and twelve, with a mean of 4.7 ± 3.0 sites. Turn over rate was high, 60%, and it did not vary significantly among colony sites type. Larger colonies were not more stable than smaller ones. Despite historically breeding at both beaches and saltmarshes, over the 15 years of study a shift in colony sites from beaches to saltmarshes and from these to dredge islands has been documented. Dredge islands, taken as a whole, were over the last years the most important breeding site in the entire lagoon.