Regeneration of anterior and posterior structures following fragmentation is a well-known characteristic of Lumbriculus variegatus, a freshwater oligochaete. Elucidation of cellular activities occurring during regeneration in oligochaetes has relied on classic histological methods. In this project, molecular and chemical approaches were used to analyze the role of cell proliferation and cell migration in L. variegatus regeneration. Mitosis was blocked through incubation of worm fragments in 2.5 mM colchicine or 25 μg/ml vinblastine sulfate. Worm fragments incubated in these drugs no longer regenerated heads or tails. Because colchicine and vinblastine may affect cellular processes other than mitosis, more direct evidence of cell proliferation was obtained by soaking regenerating worms in 5 mM bromodeoxyuridine (BrdU). At various times following BrdU treatment, worms were fixed and macerates of regenerating tissues were prepared. The dispersed cells were stained with antibodies against BrdU followed by incubation with fluorescein-conjugated secondary antibodies. Proliferation of cells, based on BrdU labeling, was observed in both regenerating heads and tails. Incorporation of BrdU into cell nuclei was observed, with extensive labeling detected in cells harvested at 120 hours into regeneration compared to tissues harvested early in the regenerative process (24 to 72 hours). To investigate the potential role of cell migration in the regenerative process, worm fragments were incubated in migration blockers, locostatin (7.5 μM) or latrunculin B (0.15 μM). Both drugs inhibited regeneration of heads and tails. The studies suggested that regeneration in L. variegatus involves both cell migration and cell proliferation and that BrdU labeling can be used to monitor these processes.