OBJECTIVE: The aim of the present study was to investigate vitamin D status among female out-patients in Saudi Arabia during the summer and winter seasons. DESIGN: Data were retrospectively collected using medical record abstraction. SETTING: A multidisciplinary hospital in Riyadh between January and December 2009. SUBJECTS: Saudi females (age ≥19 years; n 1556) attending out-patient clinics for various complaints comprised the studied population. The population was subdivided into two groups depending on the date of their visit where blood samples were collected: summer (n 659) and winter groups (n 897). The summer group was further subdivided into premenopausal (age 19-49 years; n 425) and postmenopausal subgroups (age ≥50 years; n 234). Similarly, the winter group was subdivided into premenopausal (n 543) and postmenopausal subgroups (n 354). Serum levels of 25-hydroxyvitamin D (25(OH)D) were measured using HPLC. RESULTS: The prevalence of vitamin D deficiency (25(OH)D <50 nmol/l) was high in both premenopausal and postmenopausal groups (80 % and 68 %, respectively) during the summer, as well as during the winter (85 % and 76 %, respectively). CONCLUSIONS: A high prevalence of vitamin D deficiency among Saudi female out-patients was observed throughout the year despite the routine supplementation with 10-20 μg vitamin D3 for postmenopausal women. Clinicians should seriously consider determining the vitamin D status of Saudi females routinely and prescribing them proper supplementation.