The use of moxidectin (MXD) in the treatment of small lungworm infestation (Cystocaulus ocreatus, Muellerius capillaris, Neostrongylus linearis and Protostronglylus rufescens) in sheep, was evaluated. Twenty-one sheep naturally infested with small lungworms, were divided into three groups (n = 7) and treated as follows: group A with moxidectin 1% injectable solution at a dose rate of 0.2mgkg(-1) bodyweight, group B with moxidectin 0.1% oral drench at a dose rate of 0.2 mgkg(-1) bodyweight and group C being controls. Before treatment, mean faecal larval counts were 30.7, 21.1 and 26.7 lpg in group A, B and C, respectively; 14 days after treatment respective counts were 0.4, 2.3 and 63.0 lpg, (percentage reduction after moxidectin administration >96.0%); 60 days after treatment respective counts were 0.0, 0.0 and 26.4 lpg, (percentage reduction after moxidectin administration 100%). It is concluded that treatment of small lungworm infestation of sheep can be effected by using moxidectin.