The efficacy of injectable and oral formulations of moxidectin, at a dosage of 0.2 mg kg -1 live mass was evaluated by the non-parametric method (NPM) against the most common internal parasites of sheep in 9 trials involving a total of 201 sheep. Both formulations obtained an A classification (more than 80% effective in more than 80% of the treated animals) against the third (L3) and fourth (L4) larval and adult stages of Haemonchus contortus, Teladorsagia circumcineta, Trichostrongylus colubriformis, Gaigeria pachyscelis, Chabertia ovina, Oesophagostomum columbianum and Dictyocaulus filaria, and L3 Nematodirus spathiger. The injectable formulation was similarly effective against L4 Strongyloides papillosus and the oral formulation against L4 N. spathiger and adult S. papillosus and N. spathiger. In contrast, a B classification (more than 60% effective in more than 60% of the treated animals) was obtained by the oral formulation against L4 of S. papillosus and by the injectable formulation against L4 and adult N. spathigher. Both formulations were ineffective against L3 S. papillosus, and the oral formulation also against the adults of this species.