Abstract The virucidal efficacy of peracetic acid (PAA) was evaluated against poliovirus 1, echovirus 1, coxsackievirus B5, human rotavirus, simian rotavirus SA11 and bacteriophage f 2 in a municipal sewage effluent. The results indicated relatively high concentrations of acid were required to achieve significant inactivation. Human rotavirus, which was the most resistant, required 140 ppm to achieve 99.99% inactivation. On the other hand, simian rotavirus SA11, which was the most sensitive, required only 20 ppm to achieve the same degree of inactivation. The three enteroviruses reacted similarly and the bacteriophage was slightly less resistant than the enteroviruses, especially at high concentrations of peracetic acid. The effluent did not exert a demand for peracetic acid. Temperature, organic matter and suspended solids had negligible effects on the virucidal efficacy of peracetic acid.