Fusarium solani and a binucleate Rhizoctonia were the predominant fungi in nematode and non-nematode lesions on banana roots in Honduras and Panama. In deep lesions of the main root caused by Radopholus similis, F. solani predominated followed closely in prevalence by Rhizoctonia, whereas in shallow lesions of Helicotylenchus multicinctus, Rhizoctonia predominated and F. solani was next in frequency. On necrotic small branch feeder roots Rhizoctonia predominated. In root tip dieback F. solani was the most common, then Cephalosporium and Rhizoctonia. Other fungi obtained in from 5 to 20% of the lesions included F. roseum, Cephalosporium (if tissue was macerated or fragmented before plating), Curvularia, Trichoderma, Penicillium, Nigrospora oryzae, Cunninghamella echinulata, and Botryodiplodia theobromae. Representatives of 14 other genera were inconsistently isolated as well as several nonsporing fungi. Pythium was isolated only once and Phytophthora not at all, even when selective media were used, nor was F. oxysporum encountered. Rhizoctonia and F. solani were also common inhabitants of the surface of healthy banana roots. From 40 to 60% of the Rhizoctonia isolates invaded and often killed seedlings of Musa acuminata and some isolates stunted growth of bananas in pots of methyl bromide fumigated soil. These isolates also produced brown lesions when applied to wounded banana roots growing in a mist chamber. Their contribution to root necrosis and yield decline in banana plantations remains to be determined.