The early life history of the brown shrimp (Penaeus aztecus Ives) in Galveston Bay was investigated during 1963 and 1964. Postlarvae, after entering from the Gulf, were most abundant in the channels and deeper waters as they moved into the upper reaches of the estuary. In each season of study, they were observed to spread throughout the estuary and become concentrated in surrounding marshes and bayous within about 2 weeks of first entry. After spending 2 to 4 weeks in these peripheral areas where they grew rapidly, the young shrimp, now juveniles, once again dispersed throughout the estuary before eventually returning to the Gulf. Observations also indicated that the estuarine life history phase of the brown shrimp is quite variable, with its duration probably being rela.ted in large measure to prevailing water temperature.