This study was conducted to evaluate the anthelmintic effectiveness of Albizia anthelmintica, as a first step in investigating the hypothesis that livestock self-medicate. In July 2006, an observational study was conducted with 56 young female lambs, to validate A. anthelmintica efficacy. Faecal egg per gram for Coccidia, Strongyle-type, Monezia, Strongyloides and Dicrocoelia eggs were counted and analysed. Results indicate that A. anthelmintica is effective in controlling infection with a variety of internal parasites in lambs, Monezia was the most sensitive. Furthermore, treatment of Strongyle-type worms requires a biweekly dose of A. anthelmintica as an effective deworming protocol.