Melanotropins (MSH) are involved in tanning by stimulating melanocytes via the activation of the melanocortin-1 receptor to melanin production. Its main site of production is the pituitary gland, but alpha-MSH and related ACTH peptides are produced at other sites, including the skin. It has been hypothesized that systemic levels of alpha-MSH are controlled by a varying UV radiation (UVR) exposure. A seasonal rhythm of plasma levels has been proposed by some authors. We investigated healthy females in southern Spain and central Austria in summer and winter. The alpha-MSH and ACTH-like immunoreactivity plasma levels did not present marked differences between the groups of Malaga and Linz, dark and light skin and between seasons. An association of alpha-MSH to ACTH or cortisol levels could not be observed. Individual values of alpha-MSH were shown to be relatively constant at both times of measurement (p<0.05 by rank correlation) indicating an independent personal disposition for individual systemic alpha-MSH immunoreactivity levels. Our data do not support the concept of a marked involvement of melanotropins of pituitary origin in tanning, and no seasonal rhythm was observed.