We have characterized the exon/intron organization, complete 3′ untranslated region (3′-UTR), and approximately 2.5 kb of the promoter/5′ flanking region of the mouse thrombospondin 2 (TSP2) gene. The sizes of exons and the pattern of interruption of the reading frame by introns are highly conserved in mouse TSP2 in comparison with mouse or human TSP1, a finding that suggests a close evolutionary relationship between the two genes. The TSP2 and TSP1 genes are also similar in that the 3′-UTRs of both genes contain multiple TATT and ATTT(A) motifs that might function as mediators of mRNA stability. However, the sequences of the promoter regions in TSP1 and TSP2 are very different; in particular, the TSP2 gene lacks the serum response element and the NF-Y binding site that have been implicated in the serum response of the human TSP1 gene. The structure of the TSP2 gene is consistent with emerging evidence supporting the view that TSP1 and TSP2 perform overlapping but distinct functions.