Patients with nephrotic range proteinuria have a higher risk of cardiovascular disease through qualitative and quantative changes in lipids and lipoproteins. The aim of this study was to examine the effect of omega-3 fatty acids derived from fish oil in this population. Treatment with omega-3 fatty acids in these patients was well tolerated and had a number of beneficial effects. They reduced small dense LDL concentration, remnant lipoproteins, VLDL and triglyceride level. Postprandial lipaemia was improved with an improvement in chylomicron clearance. However, we found that treatment increased LDL-C and although there was a redistribution to protective HDL2 rather than HDL3, HDL-C was not significantly increased. Furthermore, there was no improvement in endothelial function or inflammatory markers. Thus, we do not recommend treatment with omega-3 fatty acids alone for dyslipidaemia in this population of patients. The combination of omega-3 fatty acids with a statin merits further work.