From November 1995 to May 2002, the authors studied 59 children with suspected primary ciliary dyskinesia (PCD). Samples of ciliated respiratory epithelium were obtained by nasal brushing from 44 patients and by biopsy of bronchial mucosa from 15 patients. Thirty-four/Fifty-nine samples were suitable to obtain a qualitative-quantitative evaluation of ultrastructural ciliary abnormalities. Many ciliary and axoneme alterations were described. This study revealed that quantitative and qualitative ultrastructural assessment of respiratory epithelial cilia plays an important role in the differentiation between primary, secondary, and borderline ciliary abnormalities. Early diagnosis of PCD with appropriate clinical follow-up and treatment is important to prevent irreversible lung tissue damage, namely bronchiectasis.