During the period 1990-1999 84 PCD patients were identified and characterized. The expression of inherited abnormalities in primary ciliary dyskinesia after ciliogenesis was investigated in 41 patients with dynein deficiency, 6 patients with absence of the central pair of microtubules and 24 PCD patients with normal ultrastructure. In patients with dynein deficiency, the outer dynein arms counts were 1.9 +/- 1.0 in the biopsies and 1.6 +/- 0.7 after ciliogenesis. Secondary abnormalities were found in 15.8 +/- 20.4% of the transverse sections of cilia and only in 1.0 +/- 1.3% after ciliogenesis. Ciliary orientation was 28 +/- 11 degrees and 24 +/- 10 degrees respectively in biopsies and cultures. In patients with absence of the central pair this was found in 15 +/- 16% in biopsies and 21 +/- 19% after ciliogenesis. The values for the outer dynein arm were 8.4 +/- 0.3 and 8.7 +/- 0.2 and for the secondary abnormalities were 11.7 +/- 7.3% and 0.5 +/- 1.3% in the biopsies, respectively after ciliogenesis. In patients with normal ultrastructure the scores for the dynein arms were similar. Secondary abnormalities were found in 12.2 +/- 11.7% in the biopsies and 0.6 +/- 0.9% after ciliogenesis while ciliary orientation was respectively 21 +/- 7 degrees and 25 +/- 8 degrees. In conclusion, inherited abnormalities in primary ciliary dyskinesia are expressed after ciliogenesis, while secondary abnormalities are virtually absent, thereby facilitating the ultrastructural diagnosis.