The aim of this study was to examine the in vitro activity of erythromycin, josamycin, flurithromycin, miocamycin and roxithromycin on some leukocyte functional parameters. All tested macrolides did not interfere with the frequency and index of phagocytosis, nitroblue tetrazolium reduction to formazan deposits and candidacidal activity of human polymorphonuclear leukocytes (p greater than 0.05). Among macrolide antibiotics, only flurithromycin significantly inhibited neutrophil chemotaxis at a high concentration (greater than or equal to 50 micrograms/ml). All macrolides, at 10 and 50 micrograms/ml, reduced the survival of a susceptible strain of Staphylococcus aureus ingested by human monocytes.