The distribution of dopaminergic cells in the retina of sea lamprey Petromyzon marinus L. was studied with antisera against dopamine and tyrosine hydroxylase. Both antisera consistently labelled cells and processes located in the inner nuclear and inner plexiform layers. No dopamine-immunoreactive processes were observed in the external retina. The ellipsoids of photoreceptors and small bodies close to the external limiting membrane were also labelled with the tyrosine hydroxylase antiserum. It is concluded that the dopaminergic cells of the lamprey retina are amacrine cells. In addition, the presence of dopamine-beta-hydroxylase-like-immunoreactive fibres of central origin is reported for the first time.