When cells of the fission yeast, Schizosaccharomyces pombe, are incubated in medium devoid of a nitrogen source, they accelerate into cell division and differentially synthesize two polypeptides at 46 and 27 kD (named p46 and p27) after a delay of about an hour. The synthesis of p46 and p27 is transient. These proteins have no obvious cell cycle connection since they are also evident in nitrogen-starved (but not accelerated) cells of the temperature-sensitive mutant of S. pombe, wee 1·50h−. We infer from this that p46 and p27 are synthesized as a direct result of nutritional stress. The possibility that p46 and p27 represent examples of general environmental stress proteins was investigated by comparing nitrogen starvation with the heat-shock response in S. pombe. Heat-shock analysis of cells revealed the existence of two proteins of similar Mr to p46 and p27. In addition, nitrogen-starved cells acquired thermotolerance in a manner similar to heat-shocking cells. We suggest that nitrogen starvation in fission yeast induces a subset of the total array of heat-shock proteins.