Senescence marker protein-30 (SMP30) is a gluconolactonase required for vitamin C (VC) synthesis. We examined effects of VC deficiency on the mouse skin using SMP30 knockout (KO) mice. SMP30 KO or wild type male mice were weaned around day 30 of age, and fed VC-deficient diet. They were given either VC water or control water. VC deficiency for 36 days did not affect skin hydroxyproline contents, while VC deficiency for 60 days decreased the hydroxyproline levels. Levels of some collagen mRNAs were different among the groups, but did not correlate with skin VC levels. The epidermis was morphologically abnormal in VC-deficient SMP30 KO mouse at 60 days after the weaning. Interestingly, the hair cycle was not synchronized among the groups. These data suggest low susceptibility of the mouse skin to VC deficiency and involvement of VC in the regulation of keratinocyte function and hair cycle in vivo.