Dietary protein restriction and fish oil supplementation (MaxEPA) have been reported to have favourable effects on the remnant nephron model. In the present study female Munich-Wistar rats underwent 5/6 renal ablation (60 rats) or sham surgery (20 rats). The renal ablation rats were randomized one week post-surgery to receive a diet that contained either regular laboratory diet (RLD), 6% low protein diet (LPD) or 24% fish oil diet (FOD) supplementation. Mortality rates at 10 and 20 weeks post-surgery were not different amongst the RLD, LPD or FOD renal ablation cohorts. However the G.F.R. was significantly preserved in the FOD and LPD versus the RLD renal ablation rat groups. Both the LPD and FOD decreased albuminuria and gammaglobulinuria but LPD was more effective. Both dietary interventions prevented glomerulosclerosis but only LPD significantly reduced mesangial expansion. The FOD diet prevented intraglomerular fibrin formation and the LPD had no effect. The dyslipidemia noted at 20 weeks in the renal ablation group was significantly abrogated by both FOD and LPD, although only LPD prevented the heavy proteinuria. The LPD rats gained significantly less weight than the FOD and RLD cohorts. FOD exerted a significantly greater effect on blood pressure reduction than the LPD and also produced significant changes in the renal tissue phospholipids. These results indicate that protein restriction and fish oil supplementation preserve renal structure and function in the remnant nephron model but have different effects on mechanisms known to be co-factors in the progressive renal injury.