Blood levels of clindamycin-2-phosphate in dog at dosis of 10 mg/kg body weight showed the maximum of 21 mug/ml 30 seconds after one-shot i.v. administration. Continuous infusion of the antibiotic at the infusion speed of 150 and 300 ml/hour/10 kg b.w. with 6 mg/ml solution maintained blood levels of 30 and 170 mug/ml respectively. It may be recommended clinically to use lower concentration than 6 mg/ml to avoid cardiocirculatory disturbances. Four cases of surgical mixed infections with gram-positive cocci, gram-negative bacilli and anaerobes were treated with clindamycin-2-phosphate at a daily dosis of 1,200 mg intravenously and 2 of 4 cases revealed good clinical response. There was none of the haematological, hepatic, nephrontic, cardiocirculatory and allergic side effects.