The functional recovery state of renal transplants can be divided into three types: immediate graft function (IGF), slow graft function (SGF) and delayed graft function (DGF). In contrast to the well-known clinical outcomes for IGF and DGF, the pathological findings and clinical outcomes of SGF are undetermined. This study evaluated possible clinicopathological correlations in 237 patients with SGF compared with patients with IGF. IGF and SGF were defined by serum creatinine levels (IGF < 1.2 mg/day l; SGF: >/=1.2 mg/dL) at day 14 after renal transplantation. Graft biopsy was performed on this day, and pathological classification was performed using the Banff schema. The SGF group of patients (n = 121) showed higher rates of cadaver donors and male recipients than the IGF group (n = 116), but there were no significant differences in recipient or donor age, numbers of HLA mismatches, types of immunosuppressant or follow-up periods between two groups. The SGF group showed higher serum creatinine levels at discharge, and a higher incidence of acute rejection than the IGF group (24.8% vs. 8.6%, P < 0.05) and lower graft survival rates (1 year, 93.3% vs. 100%; 5 years, 85.4% vs. 98.6%, respectively; P < 0.05). The presence of acute rejection in the SGF patients indicated a significantly decreased 5-year survival rate compared with the IGF group. The SGF group of patients with borderline pathology had a higher incidence of acute rejection than the IGF group, and significant increases in the expression of mRNA for pro-apoptotic genes (Fas-ligand, granzyme B and perforin) compared with the IGF group. In conclusion, SGF represents the activated immune state and is associated with poor graft outcome. Anti-rejection treatment or modified immunosuppressive regimen may thus be indicated for patients with SGF.