Full-scale diffusion experiments were conducted to estimate coliform bacteria concentration patterns of sewage effluent from two ocean outfalls located at Pompano Beach and Hollywood, Florida. The experiments consisted of two parts: turbulent diffusion of sewage effluent, and natural die-off of coliform bacteria. Further studies were conducted before, during, and after construction of the Hollywood, Florida, ocean outfall to determine the outfall's effect on ocean ecology. For the majority of the diffusion experiments, Rhodamine dye was injected at a continuous rate into the sewage at the sewage treatment plants. The data indicated that, for the travel times of interest, initial dye concentrations can be reduced by a factor as high as 1,000. Experimental determinations of coliform die-off rates indicated that during the summer months the natural die-off is approximately two orders of magnitude greater than that during the winter. The biological studies consisted of qualitative and quantitative evaluations of the microscopic algae and protozoa of the surface waters and the ocean floor to a distance of about two miles from shore.