Aspergillus niger produced a proteinaceous hemolysin, nigerlysin © when incubated on sheep's blood agar (SBA) at both 23 and 37°C. Nigerlysin was purified from tryptic soy broth (TSB) culture filtrate and found to have a molecular weight of approximately 72kDa, with an isoelectric point of 3.45. Nigerlysin is heat stable up to 65°C but unstable at 75°C when incubated for 10min. Circular dichroic analysis revealed that nigerlysin has an alpha helical structure. Exposure of mouse primary cortical neuronal cells to 0.1μgml −1 of nigerlysin resulted in the rapid loss of their viability, approximately 50% in 24h. The IC 50 is estimated to be 0.037μgml −1 , or between 0.034 and 0.041μgml −1 at the 95% confidence level.