Sediment cores taken in November 1998 were subsequently incubated under a range of experimental conditions simulating the most important situations likely to occur in Rostherne Mere. Sediment P release into the apparently aerobic water under undisturbed conditions was estimated at 7...11 mg/(m2 d). Disturbance of the boundary layer by mixing, and/or an increase in nitrate concentration resulted in either absence of any conclusive release or even loss of the already released P back to the sediments. Estimates of P release obtained in this study are only slightly lower than the estimate obtained more than 10 years ago before sewage diversion, suggesting that rapid changes in the lakes trophic status are at present unlikely