The prevalence of clinical and subclinical rickets in Saudi children was studied in Sulimania Children's Hospital in Riyadh on admission. Among the total (16 125) admissions during 1986 and 1987 the prevalence of clinical rickets was 1.3 and 1.4% in each year respectively, and the prevalence of subclinical rickets was 3.1%. The age range of the rachitic children was 11.5 +/- 4.5 months compared with 11.6 +/- 4.7 months in control children. The majority of the rachitic children (88%) were breast-fed compared with 42.1% in control children. The plasma circulating levels of 25-hydroxyvitamin D (25-(OH)D), 1,25-dihydroxyvitamin D (1,25 (OH)2D), Calcium (Ca), Phosphorus (P) were significantly lower in rachitic than normal children. Alkaline phosphatase activity was significantly higher in rachitic children than their control counterparts.