A total of 110 agents, 109 chemicals plus gamma-rays, has been tested in a Neurospora pseudowild-type selection system for their ability to induce meiotic aneuploidy. 11 agents were positive, 47 were negative, and 52 were inconclusively tested. The system has a possible role as a short-term test for environmental agents causing human aneuploidy. The advantages of the system are its simplicity and ease of use. Disadvantages are its high variability of aneuploid frequency and an inability to distinguish mechanisms of aneuploidy.