A total of 16 episodes of peritonitis in 14 patients (9 males, 5 females), were treated with Clavulanate potentiated ticarcillin (TC), a -lactamase stable parenteral penicillin. All the pts were hospitalized and received initial loading dose of 3.2 gr intraperitoneally (i.p.) in a 6-hour 1 L exchange, which was followed by four 1 L exchanges with 320 mg/LTC. The therapy was continued for ten days. The bacteria isolated were: Staph. epid. (4), Staph. aureus (2), Strept. viridans (1), Enterococcus (1), Klebsiella Pneum. (1), Serratia (1), Enterobacter (1), Pseudomonas species: stutszeri (2), cepacia (1), fluorescens (1), negative cultures (1). Recurrence of peritonitis was seen in three patients with Pseudomonas (stutszeri (2), fluorescens (1)) peritonitis, 10-16 days after cessation of therapy. No clinical or biological side effects were seen in any patient during and/or after the therapy. These results suggest that, i.p. monotherapy of TC is effective in the treatment of CAPD peritonitis, while in cases of Pseudomonas peritonitis more specific regimens should be used.