PIP: Data from surnames and racial subgroups were obtained in 60 localities to reconstruct the history of population spread and mixing over the state of Bahia, Brazil. Using the historically significant location of Cachoeira and Sao Felix as central points, the sampled localities were distributed along 7 main paved roads. 20% of the elementary school children were selected, but only the surnames of 12,872 boys were used in the analysis. The following parameters were estimated for each of the localities: black phenotype index (BPI), which is the proportion of 3 racial classifications determined by gene frequency analysis; black cultural index (BCI) determined by the frequency of devotional surnames; and indian cultural index (ICI) determined by the frequency of animal-plant surnames; and the isolated frequency of the surname Santos. The results of regression analysis indicate a negative association between BPI and BCI and the distance from Cachoeira-Sao Felix. Although not significant, ICI increases slightly with increased distance from Cachoeira-Sao Felix. The isolated frequency of the surname Santos is associated with the BCI but does not decrease significantly with distance from Cachoeira-Sao Felix. Construction of a map characterizing each of the 60 localities by its most representative racial admixture confirms the analysis and reveals the spread of blacks toward 4 cardinal points. A review of the historical background of the state explains the migration of blacks as related to the needs for slave labor during the development of gold mining and cocoa and sugar cultivation. The higher concentrations of indian admixtures farther from Cachoeira-Sao Felix reflects their retreat to survive the incoming foreign settlers. Given the strong link between the observed diversity in the population and major historical events, it is suggested that historical reconstruction of a population be an initial step before undertaking sampling for gene frequency analysis.