The relationship between calcium and creatinine in basal urine for evaluating its usefulness as an indicator of calcium nutritional status was evaluated. Samples of basal urine were collected form a group of 5 to 12-year-old school children who followed a three-month program of dietary complementation. The calcium to creatinine ratio showed no correlation with daily total calcium intake. However, a correlation was found when intake was expressed in mg per kg of body weight (r = 0.67) and increased significantly when data were grouped according to growth rate (r = 0.85). On this basis, the Ca/Creat. ratio was analyzed as a function of weight gain (g/kg) for calcium intake: higher and lower than 10 mg/kg/day (4 = 0.82 and 0.89, respectively), the intercept of each line with the Y axis (null weight gain) being 0.096 and 0.068, respectively. These findings indicate the possibility of using the Ca/Creat. ratio in field studies as an indicator of nutritional status of the population in regard to calcium.