The literature on stream reaeration was reviewed. A recirculating loop open channel system was desiqned and experiments were performed to study the effects of average stream velocity and temperature on the mass transfercoefficient for oxyqen dissolution into "clean" water. The applicability of the apparatus to the study of the effects of surfactants was also investigated. The velocity ranged from 0.1 to 0.9 ft/sec and the temperature from 5,0 to 25.o0c. The results indicated that the mass transfer coefficient varies approximately linearly with average stream velocity and that the temperature coefficient is a variable which depends on mixinq condHions. Furthermore, it was found that the temperature dependency of the mass transfer coefficient could be expressed as either a linear or power function. Correlations expressing the mass transfer coefficient in terms of easily measurable stream parameters. were developed and compared to those found in the recent literature / Thesis / Master of Engineering (ME)