Article dans une revue: In this paper, we provide the first direct evidence on the internal structure of the migrant social network. By using a purposely designed survey on Sri Lankan immigrants living in Milan, we show that the pattern of within-group link formation is heterogeneous across immigrants, and differentiated according to the network function (i.e., accommodation, credit, job-finding). We find that migrants tend to interact with co-nationals who come from nearby localities at origin, while the time of arrival has a U-shaped effect. Once the link is formed, material support is provided mainly to relatives, while early migrant fellows are helpful for job-finding. [ABSTRACT FROM AUTHOR]