Internal migration is observed to cause major imbalances in the availability ofrneconomic and social opportunities due to fluctuation in composition and size ofrnthe population.rnA retrospective longitudinal study was conducted in Meskan and Mareko Woreda torndescribe the magnitude, patterns and differentials of internal migration in 9 PAsrnand 1 UDA sampled using probability proportionate to size. Data on variables ofrnpopulation mobility were collected by BRHP using monthly household visits for thernperiod 1987-1994. In addition, in-depth interviews with key informants, focusrngroup discussions & observation were conducted in the study sites.rnResults showed that during the 1987-1994 there was a total of 18,426 moves, ofrnwhich 9,610 (52%) were in-migrants and 8,816 (48%) were out-migrants. The sexrndistribution of both in- and out-migrants demonstrate that females outnumberrnmales. The age group with the highest percentage of internal migrants is in thernrange of 15-24 years. The observed rates per 1000 mid-year population are 36.0rnand 33.1 for in- and out-migration respectively while the net-migration was 2.9rnper 1000 mid-year population. It is observed that both in- and out-migrants arernin the active and productive age group. The pattern of population movement isrnmainly seasonal. Employment & marriage appear to be the main motives for thernpopulation movement in the area while education is also becoming important.rnThe pattern of age/sex selectivity of migration has important public healthrnimplications, in that they affect the relative size of important target group,rnsuch as children 0-4 & female 15-24 years.rnFurther detailed studies to fully understand migration streams, determinants &rnconsequences are essential