Chemical investigation on the dried material of the leech Whitmania pigra has led to the isolation of three new pteridines, including two new lumazines bearing a thieno[3,2-g]lumazine skeleton, whitmanines A and B (1 and 2) and a new pterin, 5,8-dimethylleucopterin (3). Their structures were established mainly by spectroscopic methods, especially HR-ESI-MS and NMR techniques.