The vitamin D hypothesis has received strong experimental support over the past two decades on the basis of the almost ubiquitous expression, in colon cancer cells, of vitamin D receptors (VDR) (Meggouh et al, 1991; Vandewalle et al, 1994) and 1-α-hydroxylase (Zehnder et al, 2001), which converts plasma 25-hydroxyvitamin D3 (25(OH)D) into 1,25-dihyroxycholecalciferol (1,25(OH)2D). The gene discussed is VDR; the disease is colonic neoplasm.