The main drawback of yeast biomass as a source of protein for human consumption is its high nucleic acid content. The present study deals with the development of a process for reducing the nucleic acid content of strains ofSaccharomyces cerevisiae, Candida utilis, C.tropicalisandC.lipolyticaby treating with an RNase ofAspergillus candidusstrain Ml6a. The cells were permeabilised either by heat‐treatment at 95°C for 5 min. or by treatment with chloroform for 6h followed by a heat treatment at 65°C for 3 min. The former pretreatment was sufficient forC. utilisandC.tropicalisstrains whereasS.cerevisiaerequired the latter treatment. The optimum conditions for the enzymatic treatment were a pH of 4.5–5.0, temperature of 45–55°C, incubation period of 60–90 min and an enzyme to cell ratio of 1:6,000 (w/v). Crude enzyme preparations showed a better activity than the pure enzyme. Under optimal conditions 80–85% of the total nucleic acid could be removed from yeast cells by the enzymatic treatment without any significant concomitant loss of protein.