This paper presents a statistical test of the neutral theory of molecular evolution, which predicts that regions of the genome evolving at high rates will also show high levels of polymorphism within species. The test is based on a constant-rate neutral model and requires data from an interspecific comparison of at least two genomic regions and data on intraspecific polymorphism in the same regions from at least one species. The test statistic is a goodness-of-fit statistic that measures the deviation of observed data from expected values under the neutral model. The test was applied to data from the Adh locus and the 5' flanking sequence of Drosophila melanogaster and Drosophila sechellia. The data showed a significant departure from the neutral model, suggesting the presence of balanced polymorphism in the coding region. The results indicate that the neutral model is not fully consistent with the observed data, particularly in the Adh locus, where the level of polymorphism is much higher than expected. The test is based on the assumption that mutations are neutral, that there is no recombination within loci, and that loci are unlinked. The test statistic, X², is calculated using the observed levels of polymorphism and divergence between species. The results show that the X² statistic is approximately chi-squared distributed with 2L - 2 degrees of freedom, where L is the number of loci. The study highlights the importance of testing the neutral theory using both intraspecific and interspecific data. The results suggest that the neutral model may not fully explain the observed patterns of polymorphism and divergence, particularly in regions with high levels of polymorphism. The findings support the idea that balanced polymorphism may play a role in maintaining genetic diversity in certain regions of the genome. The study also emphasizes the need for further research to understand the mechanisms underlying the observed deviations from the neutral model.This paper presents a statistical test of the neutral theory of molecular evolution, which predicts that regions of the genome evolving at high rates will also show high levels of polymorphism within species. The test is based on a constant-rate neutral model and requires data from an interspecific comparison of at least two genomic regions and data on intraspecific polymorphism in the same regions from at least one species. The test statistic is a goodness-of-fit statistic that measures the deviation of observed data from expected values under the neutral model. The test was applied to data from the Adh locus and the 5' flanking sequence of Drosophila melanogaster and Drosophila sechellia. The data showed a significant departure from the neutral model, suggesting the presence of balanced polymorphism in the coding region. The results indicate that the neutral model is not fully consistent with the observed data, particularly in the Adh locus, where the level of polymorphism is much higher than expected. The test is based on the assumption that mutations are neutral, that there is no recombination within loci, and that loci are unlinked. The test statistic, X², is calculated using the observed levels of polymorphism and divergence between species. The results show that the X² statistic is approximately chi-squared distributed with 2L - 2 degrees of freedom, where L is the number of loci. The study highlights the importance of testing the neutral theory using both intraspecific and interspecific data. The results suggest that the neutral model may not fully explain the observed patterns of polymorphism and divergence, particularly in regions with high levels of polymorphism. The findings support the idea that balanced polymorphism may play a role in maintaining genetic diversity in certain regions of the genome. The study also emphasizes the need for further research to understand the mechanisms underlying the observed deviations from the neutral model.