Human peripheral blood monocytes were found to kill Aspergillus fumigatus conidia by two hydrogen peroxide-mediated mechanisms, one being the myeloperoxidase-halide system and the other being the ferrous ion-chloride system. Murine pulmonary alveolar macrophages bound unopsonized Aspergillus fumigatus conidia in vitro. Binding was significantly inhibited by certain sugars and by mild trypsinization of the macrophage. The most effective sugars causing inhibition were Saccharomyces cerevisiae mannan, Aspergillus fumigatus galactomannan, alphamethylmannoside, N-acetylglucosamine and chitotriose. These properties pointed to a lectin-like receptor on the macrophage which bound the conidia. Mice with a thigh abscess due to Candida albicans have a heightened immune response to rabbit IgG anti-Candida antibody. In a large study of intravenous catheters used at the Clinical Center, culturing the tips of removed catheters did not aid in the diagnosis of catheter-acquired infection. The new allylamine class antifungal agent, SF 86-327, was found to give gradually increasing serum levels in patients given chronic therapy extending to one year.