Moist lesions were observed on oysters mushroom basidiocarps. The lesions were yellow, watersoaked and soft. Proliferating lesions spread all over the basidiocarp causing premature deterioration and death. Basidiocarp with symptoms were cut and surface desinfested by diluted bleach (10%). Pieces were then plated in tryptic soy agar (TSA). Symptomatic pieces of basidiocarps were placed in 2 ml of sterile distilled water, teased and streaked on TSA medium plates. Plates were incubated for 48 hours at 28EC. Single colonies forming units, were isolated and purified in TSA and King's Β medium. Koch's postulates were completed by inoculating the healthy oyster mushrooms with purified cultures. Bacterial culture broth containing approximately 109 cfii ml"1, was placed on the basidiocarp surface. Controls were made with sterile distilled water. They were placed in lidded glass dishes making a humidity chamber, and incubated at 28°C. Treatments were made in duplicates. Characteristic lesions and symptoms, were observed 24 hrs. after inoculation. Any symptom was observed in controls. The test bacteria was then re-isolated as previously described. The API Rapid NFT and BIOLOG, an automatic identification system were performed for the identification of the isolated bacteria. The isolated bacteria was identified as Burkholderia cepacia.