The study was renewed in 1992 to conduct further analysis. Based on the important findings of an inverse association between urinary markers of protein intake and blood pressure in analyses conducted on 12 of the 52 INTERSALT centers, the first component of the renewal study was to complete the biochemical and statistical analyses for the 52 centers and provide the first large population-based assessment to test the hypothesis of an inverse relationship of dietary protein to BP of individuals (with N=10,079). This relationship was also examined across populations having a wide variety of nutritional patterns (N = 52). The second major component of the study renewal was to assess the impact protein intake had on the original INTERSALT findings of a significant relation of Na, K, and Na/K with blood pressure. This component included investigation of possible interactions of Na, K, and Na/K with protein as well as with other factors shown in INTERSALT to relate to blood pressure. In addition to these main substantive questions, methodologic issues related to assessment of nutritional factors and blood pressure were further investigated.