BACKGROUND: As late provision of specialist care, before starting dialysis therapy, is believed to be associated with increased morbidity and mortality, a systematic review was undertaken to evaluate clinical outcomes relating to early versus late referral of patients to nephrology services. METHODS: Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, and EMBASE were searched up until September 2008 for studies of early versus late nephrology referral in adult (>18 years) patients with chronic kidney disease. Early referral was defined by the time period at which patients were referred to a nephrologist. FINDINGS: No randomized controlled trials were found. Twenty-seven longitudinal cohort studies were included in the final review, providing data on 17,646 participants; 11,734 were referred early and 5912 (33%) referred late. Comparative mortality was higher in patients referred to a specialist late versus those referred early. Odds ratios (OR) for mortality reductions in patients referred early were evident at 3 months (OR 0.51; 95% confidence interval [CI], 0.44-0.59) and remained at 5 years (OR 0.45; 95% CI, 0.38-0.53), both P <.00001. Initial hospitalization was 8.8 days shorter with early referral (95% CI, -10.7 to -7.0 days; P <.00001). Differences in mortality and hospitalization data between the 2 groups were not explained by differences in prevalence of diabetes mellitus, previous coronary artery disease, blood pressure control, serum phosphate, and serum albumin. However, early referral was associated with better preparation and placement of dialysis access. CONCLUSION: Our analyses show reduced mortality and hospitalization, better uptake of peritoneal dialysis, and earlier placement of arteriovenous fistula for hemodialysis with early nephrology referral.