A laboratory comparison of the effectiveness of two sediment phosphorus (P) inactivation techniques (aluminum sulfate and calcium nitrate) was made using intact sediment cores collected from Green Lake, WA. Additional treatments with Na2S, NaOH, and glucose were performed to assess effectiveness of the treatments under conditions of 1) reduced availability of Fe, 2) increased pH, and 3) organic matter enrichment, respectively. Under warm, dark, quiescent conditions both aluminum sulfate (alum) and calcium nitrate (nitrate) were equally effective in controling P release from the sediments when compared to a control. Addition of Na2S resulted in an increase in P release, but again alum and nitrate were equally effective compared to the control. Addition of NaOH resulted in an increase of P release, but alum was not as effective as nitrate in controling P release, possibly due to pH sensitivity of the aluminum hydroxy-P complex. Addition of glucose resulted in an increase of P release, perhaps due to increased gas evolution, but nitrate was not as effective in controling P release, possibly due to the availability of nitrate for degradation of organic matter and subsequent release of methane and nitrogen gas. Sediment oxygen demand (SOD) of Green Lake sediments was determined to be much less than that of sewage polluted Lake Lillesjön, Sweden, and similar to the SOD of Lake Lillesjön sediments following nitrate treatment. Sediment profiles of Fe, Mn, P, N, S, water content, and organic matter suggest that anaerobic processes were operational in the sediments. Although a recent study indicates that the overlying water does not experience episodes of reduced oxygen content, and that much of the water column increase in P can be attributed to migrating phytoplankton (primarilyGloeotrichia echinulata), possible links between sediment chemical and microbial processes and P uptake by benthic stages of phytoplankton at the sediment-water interface have not been investigated. More well planned and monitored in-lake treatments or limnocorral experiments of both alum and nitrate are needed to improve our predictions of the effectiveness and longevity of these two chemical treatments.