Radiation using gamma ray (60Co) at 0.75 KGray with dose velocity of 1.149 KGray/hour on white oyster mushroom (Pleurotus florida) mycelia yielded several mutants. Based on isozyme analysis using two enzyme markers such as esterase (EST) and acid phosphatase (ACP) showed that 3 putative mutants (PO-3, PO-4 and PO-5) among 5 mutants are positive. Even though the isozyme patterns indicated that those 3 putative mutants are positively mutated, only PO-5 showed higher productivity compared to control (PO-K) which is reflected by significantly higher number of fruit bodies, higher fresh weight and dry weight yield of three successive flush periods. It was assumed that the mutation which occurred in PO-3 and PO-4 may affect other trait(s) of the white oyster mushroom. Antioxidant analysis of those mutants indicate that mutant PO-4 has significantly higher antioxidant content compared to control (PO-K) and the two other mutants (PO-3 & PO-5). This finding leads to the possible applica¬tion of white oyster mushroom as a natural antioxidant source.