OBJECTIVE: Very few studies have addressed the relationship between number of peritoneal dialysis (PD) patients treated at a clinic (PD clinic size) and clinical outcomes. In a national prospective cohort study of incident PD patients (n = 236, from 26 clinics), we examined whether being treated at a larger PD clinic [>50 PD patients (n = 3 clinics) vs <or=50 PD patients (n = 23 clinics)] was associated with better patient outcomes, including fewer switches to hemodialysis, fewer cardiovascular events, lower cardiovascular mortality, and lower all-cause mortality. METHODS: Multivariable Cox models were used to assess relative hazards (RHs) for modality switches, cardiovascular events, cardiovascular deaths, and all-cause deaths by PD clinic size. All models were adjusted for demographics, comorbidities, laboratory values, and clinic years in operation. RESULTS: Being treated at a clinic with >50 patients was associated with fewer switches to hemodialysis (RH = 0.13, 95% CI 0.06 - 0.31) and fewer cardiovascular events (RH = 0.62, 95% CI 0.06 - 0.98). No associations of PD clinic size with cardiovascular or all-cause mortality were seen. CONCLUSION: PD patients treated at clinics with greater numbers of PD patients may have better outcomes in terms of technique failure and cardiovascular morbidity. PD clinic size may act as a proxy of greater PD experience, more focus on the modality, and better PD practices at the clinic, resulting in better outcomes.