Eight out of nine species of snow algae occurring on Mt Philistine, Arthur's Pass National Park, are new records for New Zealand. Chlainomonas kolii, reported previously in snow beneath tree canopies in the USA, is responsible for blooms which colour the snow red. Chloromonas rubroleosa, which is found in red snow dominated by C. kolii, also occurs in continental Antarctica. Three other species of Chloromonas, including the relatively common bipolar alga previously known as Scotiella antarctica, occur in other snowfields on the mountain. The widely reported Raphidonema nivale was identified in cultures from many snow samples. Two species of chrysophyceans, Chromulina cf. elegans and Chrysophyceae sp. 2 (a cyst, of which the life cycle is not understood) occur in Mt Philistine snow. The few previous investigations of New Zealand snow algae have suffered from lack of culturing and observation of living material. Results presented here show that many more sites require detailed study using these techniques to improve our understanding of the biogeography of New Zealand snow algae, and for comparison with floras elsewhere to be meaningful.