Osteoporosis is 8 major public health problem. It is characterized by decreased bone mass and increased susceptibility to fractures. Inadequate calcium intake is one of the factors relating to osteoporosis. The study on calcium status and its relationship to bone status in Thai population has not yet been reported. Therefore, the calcium and bone status of the urban Thai population, the sources and amount of calcium intake, serum level and urinary excretion of calcium, anthropometric dimension, body composition, and bone status in 396 healthy Thais (153 men, 243 women), age 20-$0 years, were studied. The mean+SD of daily calcium intake was 361 +,- l68 mg (men 366 +,- 160, women 359 +,- 189 mg). The median and mode of daily calcium intake were 319 mg (men 341, women 309 mg), and 206 mg (men 206, women 280 mg), respectively. However, there was no significant difference in the calcium intake between sexes and among all age groups within the same sex. Majority of the subjects (67%) consumed less than 400 mg calcium/day (low intake) and 31% consumed between 400--800 mg/day (moderate intake) whereas only 2% of the subjects had a calcium intake of more than 800 mg/day (high intake). The high, moderate, and low calcium intake groups consumed calcium from milk amounting to 46.9, 28.7, and 12.7% of their total daily calcium intake, respectively. Women consumed milk and its products as calcium source more than men. As expected, bone mineral content (BMC) and bone mineral density (BMD) decreased with advancing age. In this study, the role of calcium intake on the changes of BMC in the middle age group (3049 years) was not evident. However, there were positive relationships between calcium intake and BMC in young adults (20-29 years) and old age groups (70-80 years). It was shown that changes in calcium intake affected bone status of the young adults and elderly. In addition to sex difference, factors relating to bone mineral content (BMC) were age, height, weight, distal wrist circumference (DWC), potassium intake, and urinary calcium. Multiple regression analysis revealed the correlation coefficient of these factors and BMC to he 0.85. It seems that calcium intake between 200-400 mg/day may be adequate to support bone status for the Thai middle age (30-49 years) while higher calcium intake is beneficial in other groups.