In replication of other studies, the natural decrease of Texas population was examined in terms of the effect of migration and fertility. Utilizing Texas and U.S. vital statistics and the 1970 U.S. Census of Population, Texas population trends were analyzed for the 1968-72 period by dividing the 254 Texas counties into: (1) 65 natural decrease counties (those registering more deaths than births); (2) 132 low natural increase counties (those below the state average); (3) 57 high natural increase counties (those above the state average). Findings indicated natural decrease counties: (1) were smaller; (2) consituted less than 6% of the population; (3) were primarily rural; (4) experienced net-in-migration gains in 18 of the 65 counties; (5) had a population with an average median age of 41.1 years; (6) had a low proportion of Spanish-speaking population; (7) had a lower fertility level than the increase counties, but had a level above replacement levels. It was concluded that: (1) the presence of Spanish-speaking populations influenced fertility differentials, since counties with large Spanish populations experienced high levels of natural increase in spite of high levels of out-migration because of high fertility; and (2) migration trends for longer time intervals and by age should be examined to determine the effect of migration on age structure and natural decrease. (JC)