Physical, chemical, biological, ecological, and aesthetic aspects of the Wairakei Power Plant are examined, in varying detail, but with primary emphasis on the chemical and thermal effluents. When flows are average or higher in the Waikato River, the Plant's environmental effects are not overly severe. However, operating requirements for the Waikato Hydro-electric System are such that the Plant sporadically produces wastes that may affect the human and natural environment adversely. These adverse effects are not presently too serious, but suggestions are made for improving the Plant's overall environmental performance. Although the point is not discussed in detail, it is clear from the results of the study that any additional thermal plants on the Waikato could strain the river's absorptive capacities severely, unless alternative disposal techniques are used for the various effluents.