This Paper examines changes in the sex ratio's age patterns in various censuses. To this end, while analyzing factors influencing Iran's sex ratios using Davis method, the age-specific changes in the sex ratios in 1966-2006 period has been examined and the pattern in Iran are compared with other regions of the world. Analyzing the sex ratios using Davis method shows that the expected trend of changes in sex ratios' age pattern, based on Coale & Demeney life tables (west model) differs from the observed pattern in Iran. Research findings also show increase in the sex ratio in ages above 60, which contrasts with the trend observed in Europe, North America and Africa, which shows decreasing age ratios in older ages because of the impact of male cumulative mortality excess effects. Similarity between the pattern observed in Iran and the related trend in South-East Asian countries is due to the effects of similar cultural, social and economic contexts. These similarities create certain demographic regime in these regions whose characteristics can be understood by considering the cultural variables along with other factors.