The clinical appearances of infections in 128 patients caused by the mould fungi Hendersonula toruloidea (102) and Scytalidium hyalinum (37) are described. All the patients originated from the tropics or subtropics but those infected with S. hyalinum came from either the Caribbean or West Africa. Forty-one per cent of those studied had a concurrent dermatophyte infection. While the clinical features of Hendersonula and Scytalidium infections resembled those seen in 'dry type' Trichophyton rubrum infections, there were a number of distinctive features. These included the absence of dorsal infection on the feet, lateral and distal onychomycosis with extensive onycholysis and the development of paronychia on the fingers. The majority of affected patients showed no serious underlying abnormality or predisposing skin disease which could facilitate invasion. The routine incorporation of cycloheximide, which inhibits the growth of these organisms, in mycological media may explain why they are infrequently diagnosed.