Motoneurons supplying the common peroneal nerve in the dog were identified by the retrograde horseradish peroxidase method. They were distributed within two discrete cell columns (columns 2 and 2') in the 6th and 7th lumbar segments. The extensor digitorum longus muscle was represented in the dorsolateral part of column 2; the peroneus longus muscle in the ventrolateral part and the tibialis cranialis muscle in the intermediate lateral part. The medial half of column 2 contained motoneurons supplying the superficial peroneal nerve. Column 2', which was situated dorsomedially to column 2, contained motoneurons innervating the extensor digitorum brevis muscle.