The incidence of postharvest spoilage of banana fruits in 12 towns (Tinsukia, Dibrugarh, Sibsagar, Jorhat, Guwahati, Goalpara, Dhubri, Mongaldai, Tezpur, North Lakhimpur, Diphu and Silchar) in Assam, India, was studied. The degree of spoilage of fruits of cultivars Jahaji and Chenichampa reached 19.60 and 18.07%, respectively. Aspergillus terreus, Botryodiplodia theobromae, Fusarium oxysporum, F. moniliforme [Gibberella moniliformis], Penicillium italicum, Rhizopus stolonifer, Sclerotinia sclerotiorum and Trichothecium roseum were isolated from the rotten fruits of both cultivars from all locations. B. theobromae was the major pathogen causing postharvest spoilage of banana fruits. The growth of the isolates at varying temperature (10, 20, 30, 40, 50 and 60°C) and pH (40, 50, 60, 70, 80, 90 and 100%) was investigated. The isolates showed optimum growth at 25-30°C and could initiate infection at 40% relative humidity. The percentage of rot increased with increasing relative humidity. The efficacy of benomyl (100 ppm), Bavistin [carbendazim] (100 ppm), Captan (2000 ppm), Dithane M-45 [mancozeb] (1000 ppm), Mycostatin (500 ppm) and Fytolan [copper oxychloride] (1000 ppm) as pre- and post-inoculation treatments against the fungal isolates was evaluated. Fruits were dipped in fungicide solutions before or after the inoculation of fungi and incubated at 27±1°C for 10 days. Benomyl as post-inoculation treatment completely controlled the fungi. Pre-inoculation treatment with benomyl reduced the infection of fruits by Aspergillus, Penicillium, Fusarium and Rhizopus by more than 75%. Captan as post-inoculation treatment also resulted in the complete control of Rhizopus rot. Bavistin completely controlled decay in Chenichampa fruits except that caused by Rhizopus.