S L: M M A R yNitrite uptake in the nitrate-assimilating yeast, Candida nitratophila, was inhibited completely by addition of nitrate or ammonium to cultures at pH SO. Nitrite assimilation m these cultures was also completely dependent on the availability of a suitable carbon source (glucose). In cultures at pH 5'0, neither nitrate nor ammonium inhibited nitrite uptake completely. In these cultures, some nitrite was assimilated in the absence of a carbon source. Carbon-deficient cultures at pH 5'0 were able to reduce nitrite to ammonium but excreted this ammonium without further assimilation. E\idence for the uptake of nitrite by passive diffusion and by active transport via the nitrate uptake system is discussed.