OBJECTIVES: To determine the treatment costs of suspected invasive pneumococcal diseases (IPD) among children in Khanh Hoa Province, Vietnam. METHODS: This study was an incidence-based cost-of-illness analysis employing a bottom-up approach using the health system perspective.  Patient costs were drawn from the hospital-based surveillance program at Khanh Hoa General Hospital during 2005-2006.  The direct medical cost is the patient charge adjusted by the cost-to-charge ratio (1.14).  Costs were converted from Vietnamese currency (dong) to US dollar (VND15976.83 = $US 1.00, 2006).  In the surveillance program, standardized screening criteria were used to identify children < 5 years of age with signs and symptoms of IPD.  Treatment costs were analyzed using descriptive statistics and multivariate regression analysis was used to identify important cofactors influencing treatment costs. RESULTS: Nine hundred eighty children were included in this analysis. Their mean age was 12. 7 months (±11.4) and 57% (n=577) were male. The patients were classified as suspected pneumonia (80%); meningitis (8%); very severe pneumococcal sepsis (3%); and other diseases (9%) as well as probable (5%); chest radiograph (CXR) confirmed (54%); probable severe (7%); CXR-confirmed severe (34%); probable very severe (3%); and CXR-confirmed very severe pneumonia (6%).  Treatment costs of suspected pneumonia, meningitis, very severe disease, and other diseases were US$31, $57, $73 and $24, respectively. In the multivariate regression analysis, case category, age, history of antibiotic use, and fever had statistically significant effects on the total treatment cost. CONCLUSIONS: Treatment costs of suspected IPD are considerable for Vietnamese children and appear to higher for disease with greater clinical severity.  These data will be helpful to understand the economic burden of suspected IPD as well as the cost –effectiveness of pneumococcal conjugate vaccine for routine childhood immunization in Vietnam.