The purpose of this study was to investigate the secular trend of menarche age within the last 35 years in an immigrant urban city in Turkey-İzmir. We found the mean age at menarche as 13.10±1.18 years for 121,257 women. The reported mean age at menarche showed a decreasing trend over time. For women born before 1963 (≥40 years of age), the mean age at menarche was 13.08±1.21 years. For women born from 1964-1973 (30-39 years of age), the mean age at menarche was 13.12±1.19 years. For women born from 1974-1983 (20-29 years of age), the mean age at menarche was 13.11±1.18 years, and for those born after 1984 (15-19 years of age), the mean age at menarche was 13.06±1.16 years (p=0.000). When divided according to socioeconomic status, the mean age at menarche was 13.11±1.11 in the high socioeconomic group, 13.22±1.25 in the middle socioeconomic group, and 12.75±1.02 in the low socioeconomic group (p=0.000). In conclusion, in the Turkish population, the mean age at menarche has decreased from 13.12 to 13.06 over the past 30 years, and the mean age at menarche was lower in the low socioeconomic group.