Wnt genes encode a family of secreted proteins having oncogenic potential and important roles in developmental processes. We report the isolation of cDNAs for a novel murine Wnt gene, Wnt10a, and for two alternatively spliced transcripts of Wnt10b, as well as analyses of the expression patterns of these genes in adult and embryonic tissues. Wnt10a and full length Wnt10b encode relatively closely related (62% identity) Wnt proteins containing the 24 cysteines characteristic of most Wnt proteins. The deduced protein encoded by the alternatively spliced Wnt10b transcript lacks a central region encompassing 25% of the full length isoform. Both Wnt genes were widely expressed in the adult, although the levels of expression varied significantly. Wnt10a RNA was most abundant in adult brain with a high concentration in the pituitary gland, and expression of Wnt10b was highest in adult lung and uterus. RNAs of both genes were detected in thymus and spleen, tissues not previously reported as sites for Wnt gene expression. Wnt10a and Wnt10b expression broadly peaked at approximately 13.5 and 15.5 days of gestation, respectively, and Northern blot analyses of RNAs from dissected embryos revealed that expression of both genes was strongest in the face, limbs and skin and that Wnt10a was also expressed in the liver, the major site of hematopoiesis in the embryo. These expression patterns suggest that Wnt10a and Wnt10b may function in various tissues of the adult and embryo with notable expression in tissues responsible for the formation and maturation of blood cells, in the pituitary gland (Wnt10a), and in the face, limbs and skin of developing embryos.