Neutrophil chemotaxis. Neutrophil chemotaxis was measured to zymosan-activated serum as described in Materials and Methods. There was significantly reduced chemotaxis after 5 days of G-CSF therapy (*P = .0001). There was also a trend toward less nondirected migration (buffer) after G-CSF therapy, but this difference was not significant (P = .18). Results are expressed as distance migrated through filter (microns) and represent mean ± SEM, n = 8.