(1 --> 3)-beta-D-glucan, a characteristic fungal molecule, is known to increase in blood in invasive candidiasis, aspergillosis and cryptococcosis. This report shows that the plasma glucan concentration was also elevated in four patients infected with Fusarium, Trichosporon beigelii, Saccharomyces cerevisiae and Acremonium. In three of the patients, the elevation preceded positive blood cultures by 5-17 days, and in one of them it even preceded the onset of fever by 6 days. In a fourth patient, the glucan level decreased with clinical improvement. Plasma (1 --> 3)-beta-D-glucan determination appears to be useful also for diagnosis and follow-up of these unusual deep mycoses.