This paper describes an instrument developed in Italy by the ISMU Foundation to measure the level of integration of immigrants present in the country. The instrument consists of an index based on data collected by means of a structured questionnaire. The paper first describes the technical characteristics of this instrument and the main results obtained from its first, experimental use with the administration of over 12,000 interviews in Italy. There follow some critical notes on the limits and potential of the application of synthetic indexes in the analysis of migratory processes, and particularly in study of the integration of immigrants.