SummaryMigration of human peripheral blood granulocytes in response to microfilariae of O. volvulus was demonstrated using modified Boyden chambers. Granulocyte migration was significantly enhanced when microfilariae were preincubated with heat‐inactivated immune serum (ΔIS), then added to a fresh serum source (P<0.025). This effect was not seen when microfilariae were incubated in medium alone, in ΔIS alone, in ΔIS plus C4‐deficient guinea‐pig serum, or in fresh serum alone. There was no significant difference between the response of cells from O. volvulus‐infected donors and that of cells from normal volunteers. Likewise, there was no significant difference between the migratory response seen toward nodule‐ versus skin‐derived microfilariae. These results suggest that the host inflammatory response to O. volvulus microfilariae is mediated in part by chemotactic factors generated by antibody and complement interaction with the organism and, furthermore, that these factors are product(s) of classical complement path