Chronic benign neutropenia is seen in children and is usually detected when repeated occurrence of infectious diseases such as acute otitis media, gastroenteritis, tonsillitis and skin infection, are observed. It is rarely diagnosed as a result of detection of oral lesions. A case of chronic benign neutropenia diagnosed during evaluation of severe stomatitis in a 20-month-old Japanese girl is described in this paper. In order to establish a treatment plan, we examined a dental plaque sample by PCR method, but found no specific causal bacteria. When pediatric dentists encounter repeated gingivitis or stomatitis, the possibility of hematologic disease should be considered.Key words Chronic benign neutropenia, Gingivitis, Oral bacteria, Polymerase chain reaction, Stomatitis. © 2005, The Japanese Society of Pediatric Dentistry. All rights reserved.