Phosphorus external and internal loading to Pine Lake was estimated and potential restoration measures were recommended. External sources contributed approximately 57 percent of the total phosphorus load, and internal sources the remaining 43 percent. External and internal loading together exceeded the critical level expected for a mesotrophic state. About one-third of the external load, or about 20 percent of the total, entered through a channel draining a wetland. Total phosphorus concentration in this source was more than six times that in the lake; nearly 90 percent was soluble reactive phosphorus. This inflow will be diverted to the outflow in 1986. Another one third of the external load represented a “residual” occurring during the wet season. This was attributed to cultural activities, namely leachate from near-shore septic systems, although direct evidence was limited. About 35 percent of the total load entered from-internal sources, largely from littoral sediments and photosynthetically elevated pH during the spring algal bloom. This source of input is particularly important because it enriches the epilimnetic waters when the potential for increased algal growth is great. Wetland diversion and correction of failing near-shore septic systems should result in a lower mesotrophic state and greater than a 60 percent reduction in total phosphorus during the spring bloom period if productivity is reduced sufficiently to prevent elevated pH. The success of restoring Pine Lake depends on whether or not internal loading during the spring bloom is substantially reduced. A “worst-case” improvement is only a 12 percent reduction in total phosphorus during the spring bloom maximum, which assumes no change in the pre-diversion littoral sediment phosphorus release rate. However, diversion alone should result in less productivity, lower pH, and less sediment phosphorus release.