We report two cases of Werner's syndrome (WS). First, a 42-year-old Japanese man was referred on suspicion of systemic sclerosis (SSc) because of scleroderma-like skin atrophy and foot ulcers. Second, a 51-year-old woman with malignant fibrous histiocytoma was referred on suspicion of premature aging syndrome. Because both patients had many typical manifestations compatible with WS, we made a clinical diagnosis of WS. Genetic analyses revealed a homozygous mutation, an A deletion at nucleotide 3677 of WS gene (WRN) in the first case and a homozygous mutation, a G to C substitution at one base upstream of exon 26 of WRN in the second case. Both mutations were consistent with those previously reported in Japanese WS patients.