In recent years scientists have hypothesized that low blood vitamin-D levels play a role in the development of autoimmune diseases, including Crohns disease. The purpose of this study is to examine whether vitamin-D is effective in keeping remission in inactive Crohns Disease (double blind placebo controlled trial). The patients who have active disease in the placebo group (reach primary endpoint), will in an open setting receive a higher single dose vitamin-D and the effect will be measured within 4 weeks.