This article examines the determinants of immigrants’ language proficiency and language use, two dimensions of language which have so far remained rather separate in the literature. The underlying question is whether similar or different patterns underlie these two aspects of language. The data are from large-scale, repeated cross-sectional surveys specifically designed to study Turkish and Moroccan immigrants in the Netherlands. We focus on Dutch speaking skills and Dutch language use with the partner. The results show that although speaking ability and language use with the partner generally go hand-in-hand, the correlation is modest. Language proficiency and language use are equally affected by migration motive, settlement intentions and ethnic concentration in the neighbourhood. Dutch language use with the partner is strongly and directly affected by the Dutch language skills of the partner. Age at migration and education are more important for language proficiency than for language usage.