In a previous study, polymorphonuclear (PMN) leukocyte chemotaxis in vitro was inhibited by therapeutic concentrations of griseofulvin. In the present investigation, PMN migration in a casein gradient was studied in a cell suspension containing serum collected before and after a therapeutic peroral single-dose of griseofulvin. The PMN migration in vitro was not influenced significantly by the presence of griseofulvin-containing serum. It is suggested that peroral griseofulvin treatment has neglibible effect on PMN chemotaxis in vitro.