This in vitro study investigates the phagocytosis and killing rate of Candida albicans blastospores and germ tubes by polymorphonuclear leukocytes. Suspensions of C. albicans blastospores and germ tubes were incubated for 60 and 150 min with a neutrophil suspension. The rate of phagocytosis was found to be 92 +/- 3% for blastospores, but only 9.5 +/- 2.5% for germ tubes. The candidacidal activity rate was 29 +/- 6% for blastospores, but only 5.5 +/- 1.5% for germ tubes. Electronmicroscopically, cytoplasmic and plasma membrane alterations of phagocytized yeast cells lying in phagosomes were observed. Short germ tubes surrounded by a phagosomal membrane were found in neutrophils. Older, longer germ tubes were seen in an extracellular position. Usually, several neutrophils were adjacent to these long tubes. Obviously phagocytosis could not take place owing to the size of the germ tubes. The findings indicate that the transition of the yeast phase to the mycelium phase in a case of Candida infection may be a mechanism enabling the parasite to escape phagocytosis by the host.