Abstract: The natural course of acute immune thrombocytopenic purpura (ITP) in infants is poorly described in the literature. A retrospective study of 17 consecutive patients <1 yr of age admitted and treated for acute ITP between 1996 and 2005 was conducted. We investigated their demographics, vaccination history, clinical features, laboratory examinations, response to treatment and long-term outcome. There were 11 male and six female infants. Their ages ranged from 24 d to 12 months with a median of 3 months. All infants presented with petechiae and/or ecchymoses. Fourteen cases had platelet counts below 20 × 109/L at the time of admission. They all had good response to a single course of treatment (14/17) or multiple courses of treatment (3/17). None had progressed into chronic ITP. Seven infants had a causal relationship with immunization, five associated with hepatitis B, one diphtheria–pertussis–tetanus, one diphtheria–tetanus–acellular pertussis-inactivated poliovirus vaccine-conjugated Haemophilus influenza vaccines. These seven infants responded to treatment within 3–9 d after therapy with intravenous immunoglobulin, high-dose methylprednisolone or oral steroids. Re-boosters with vaccines revealed no recurrence of the disease in all of these seven patients. The study suggests that further immunization is not contraindicated in infants experiencing acute ITP associated with vaccines.