To conserve biodiversity, it is necessary to understand how species are distributed and which aspects of the environment determine distributions. In large parts of the world and for the majority of species, data describing distributions are very scarce. Museums, private collections and the historical literature offer a vast source of information on distributions. Records of the occurrence of species from these sources are increasingly being captured in electronic databases and being made available over the internet. These records may be very valuable in conservation efforts. However, there are a number of limitations with museum data. These limitations are dealt with in the first part of this review. Even if the limitations of museum data can be overcome, these data present a far-from-complete picture of the distributions of species. Species distribution models offer a means to extrapolate from the limited information that we have in order to estimate the distributions of species over large areas. In the second part of this paper, we review the challenges of developing species distribution models with museum data and describe some of the questions that species distribution models have been used to address, focusing on studies that have used museum data. Given the rapidly increasing number of museum records of species occurrence being made available over the internet, a review of their usefulness in conservation and ecology is timely.