The increasing need of reliable and detailed information at a regional and subregional level poses some challenges related with the measurement of tourists flows, for tourism destination management, planning and promotion purposes,. The aim of this work is twofold; first, it intends to analyse and discuss the main features and limits of the official border surveys conducted in the majority of world’s countries, within the framework of Time Location Sampling (TLS) design; second, it suggests the implementation of TLS design at a subnational level, by presenting the sampling design of the survey on incoming tourists in Sicily, carried out between 2009-2010, aimed at estimating the unobserved tourism and at analysing tourist mobility in the island