Vitamin D deficiency has been linked to hypertension. Although vitamin D deficiency is common in tropical regions, no data on its association with hypertension were available. We randomly selected 137 cases and controls whose plasma in 1985 was available for the assessment of vitamin D status and calculated the odds ratio of having hypertension in 1997. In all, 36% of the participants were vitamin D deficient. The odds ratio of having hypertension was marginally significant for vitamin D deficiency (0.59, P=0.05) and statistically significant for body mass index (BMI)-defined overweight (1.8, P=0.02). The inverse relationship between vitamin D deficiency and hypertension became statistically significant after further adjustment for BMI, high-density lipoprotein cholesterol and triglyceride (0.55, P=0.03). Stepwise regression identified BMI-defined overweight and vitamin D deficiency as the variables of significance in relation to hypertension. Our data suggest that vitamin D deficiency, although not a rarity in Thailand, was not associated with an increased risk of developing hypertension in Thai people.