Atropa belladonna and Echinacea angustifolia have been used in homeopathy as modulators of inflammatory processes, in simple potency or ‘accord of potencies’, as recommended by homotoxicology. We evaluated their effects on leukocyte migration and macrophage activity induced by experimental peritonitis in vivo. Mice were injected (i.p.) with LPS (1.0 mg/kg) and treated (0.3 ml/10 g/day, s.c.) with different commercial forms of these medicines. Echinacea angustifolia D4—a simple potency preparation—and Belladonna Homaccord®, Belladonna Injeel®, Belladonna Injeel Forte®, Echinacea Injeel® and Echinacea Injeel Forte®—all in ‘accord of potencies’—were tested.The association of A. belladonna and E. angustifolia in ‘accord of potencies’ produced an increase of polymorphonuclear cell migration (Kruskal-Wallis, P=0.03) and a decrease of mononuclear cell percentages (Kruskal-Wallis, P0.04), when compared with control, mainly in preparations containing low potencies. The proportion of degenerate leukocytes was lower in the treated groups, compared to a control group (P0.05). The treated groups showed increased phagocytosis (P0.05), mainly in preparations containing high potencies. Our results suggest that A. belladonna and E. angustifolia, when prepared in ‘accord of potencies’, modulate peritoneal inflammatory reaction and have a cytoprotective action on leukocytes.