We have designed the filter paper absorption method(FPM) for collecting and transporting urine samples and used the method for the determination of urinary excreation of Na, K and creatinine(Cr.) in the epidemiological surrvey.

A fixed or free amount of urine samples were absorbed with No.6 Toyo filter paper (Toyo Roshi Co., Ltd.), wrapped in aluminium foil after drying naturally in room temperature, transported to the laboratory and were stored in a cold dark place. Na, K and Cr. were extracted from the filter paper with blank solution. Na, K and Cr. concentrations were measured by flame photometry and Jaffe's method, respectively.

1) In order to estimate the reginal salt intake in Japan causal urine samples from 3-year-old infants were collected from 95 public health centers in 47 prefectures, 4,535 filter paper strips were measaured and urinary Na/K(mEq/mEq), NaCl/Cr.(g/g) and K/Cr.(g/g) were calculated. The results (M±S.D.) were 3.40±2.52, 18.49±11.18 and 4.62±2.81 respectively. Urinary Na/K and NaCl/Cr. from rural areas were significantly higher than urban areas, while K/Cr. was not significant. Reginal NaCl/Cr. and K/Cr. were higher in North of Japan and North Kyusyu and lower in Kinki district. Urinary NaCl/Cr. were significantly correlated with salt intake by National Nutrition Survey and with age-adjusted death rate from cerebrovacular disease.

2) We have analysed Na, K and Cr. concentration of urine samples from Gidra in Papua New Gunea and Fijian in Fiji. Causal urine samples were absorbed in a filter paper, wrapped in aluminium foil after drying in room temperature, transported to the laboratory. The results(M±S.D.) were 1.14±1.36(Na/K), 2.18±2.18(NaCl/Cr.), 1.89±1.32(K/Cr.) in Gidra(N=320)and 1.54±1.04, 4.75±2.78, 2.28±0.97 in Fiji-Fijian(N=178) and 3.00±2.24, 7.42±4.73, 1.87±0.93 in Fiji-Indian(N=87), respectively.