Conflicting ventilatory defects have been reported in children with sickle cell disease (SCD). In Kuwait, the disease is relatively mild with a low incidence of acute chest syndrome and other complications, presumably due to the Arab-Indian haplotype chromosomal background and elevated Hb F levels. There have been no previous studies of pulmonary function in patients with this haplotype. Pulmonary function test (PFT) was carried out on 28 steady state children with SCD (21 homozygous sickle cell (SS), seven S beta(o) thal) and two group of controls: 17 age- and sex-matched healthy children and 10 children with HbH disease. The charts of the SCD patients were reviewed for frequency of acute chest syndrome and vaso-occlusive crisis. The mean values of forced vital capacity (FVC) (83.2 +/- 11.9 vs. 91.2 +/- 11.7) and vital capacity (VC) (81.5 +/- 11.8 vs. 90.5 +/- 10.9) were significantly lower in the SS patients compared with healthy controls (p < 0.05). Similarly, these values were significantly lower than in those of the HbH group (p < 0.001 for VC and p < 0.01 for FVC). The mean forced expiratory volume in 1 s (FEV1) was lower in SS patients (86.4 +/- 11.5) compared with healthy controls (94.2 +/- 14.2), but the difference was not significant (p = 0.07). Also, the FEV1 was significantly lower in SS patients than in the HbH group (p < 0.001). There was no significant difference in the PFT parameters between SS patients with acute chest syndrome and those without. Although patients with frequent vaso-occlusive crisis had lower PFT parameters, the differences were not significant in comparison to those with infrequent crisis. This study revealed an early restrictive and obstructive pulmonary function pattern in steady state children with SCD. The finding also indicates that the changes of PFT parameters in SS patients could not be attributed to anaemia per se as patients with HbH who also have chronic anaemia did not show similar changes. This observation underscores the early occurrence of pulmonary involvement, even in patients with an otherwise relatively mild SCD.