Abstract: By means of cytogenetic methods such as micronucleus test, chromosome aberration analysis and sister chrornatid exchange analysis, potential mutageneticity of the nuclear polyhedrosis virus of Ectropis obliqua, a lepidopte.rous pest of tea gardens, was comprehensively assessed. None of the experimental results gives evidence of Eo NPV mutageneticity either in vivo or in vitro. Bo NPV causes no damage to chromosomes of man and vertebrates