A prospective observational study examining the incidence and microbiological aspects of peritonitis complicating acute intermittent peritoneal dialysis (IPD) was performed. A total of 145 acute IPD treatments were included involving 112 patients. The majority of patients suffered from acute kidney injury (72.3%) secondary to sepsis. Peritonitis occurred in 31 treatment sessions, giving a frequency of 21.4% of procedures performed. The mean interval between starting dialysis and the first sign of peritonitis was 2.9 days, with 58% of cases occurring in the Intensive Care Unit. Frequent catheter manipulation/repositioning and leakages were identified as significant predisposing factors for peritonitis, and the risk of peritonitis was increased with longer duration of IPD. Gram-negative infections were more common than Grampositive infections. The use of systemic antibiotics did not prevent the development of peritonitis.