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Production of fructose is important especially in the food industries where fructose is used as a sweetener in preference to sucrose. This work studied some cultural conditions for the production of invertase by Aspergillus niger. In a preliminary experiment, all isolated fungal spores were incubated in 0.2 M sucrose solution and the spores of Aspergillus niger produced the highest invertase activity of 72.8U/mg protein and was therefore selected for further work. Inversion of sucrose by spores of Aspergillus niger was then studied after various incubation periods. Incubation for 6 hours with shaking was best for enzyme production at which 94.6 U/mg protein of the enzyme was produced. Enzyme yields at 1 and 2 h of incubation were very low while incubation for elevated periods of 7 and 8 h resulted in moderate enzyme yields of 68.3 and 60.4 U/mg protein respectively. Lower sucrose concentrations of 0.3 and 0.4 M were almost completely inverted while higher concentrations showed decreases in enzyme activities. Invertase from Aspergillus niger was incubated at various temperatures and it was found that at 10oC, only 26.5 U/mg protein of the enzyme activity was produced. This level increased gradually with increases in temperature until 30oC at which the highest enzyme activity of 72.8 U/mg protein was produced. This level reduced progressively with increases in temperature until it reached a temperature of 50oC at which very low activity was obtained. It was shown that pH 5.0 was the best for invertase production by the test fungus. [ABSTRACT FROM AUTHOR]