An association between IgE receptor FcepsilonRIbeta polymorphism and atopy has been reported and proposed to be maternally transmitted. In a previous communication we reported high prevalence of the IgE receptor FcepsilonRIbeta variant (Leu 181/Leu 183) in Kuwaiti Arabs with asthma. This study investigates the association of this variant with parental consanguinity, maternal vs paternal inheritance, gender, and severity of asthma in 52 Kuwaiti families in whom at least one person had asthma. Using an allele refractory mutation screening (ARMS) test, blood (from 212 subjects, including asthmatic children, their parents and siblings) was tested for the presence of the normal and variant sequence of the IgE receptor FcepsilonRIbeta [homozygous normal sequence (Ile 181/Val 183, NN), the variant sequence (Leu 181/Leu 183, LL) and the heterozygous state NL]. In the 52 families 99 subjects were asthmatic. The consanguinity rate was 42 per cent which is similar to the 54 per cent reported for the Kuwaiti population as a whole. There were slightly more asthmatic fathers (27 per cent) than mothers (21 per cent) but this difference is not significant. The male to female ratio amongst the asthmatics was 1.5:1 and there was no gender effect on the frequency of the homozygous variant. Fifty-eight subjects (59 per cent) had severe and 41 (41 per cent) moderate asthma. Significantly more patients with severe asthma (58 per cent) were homozygous for the variant (Leu 181/Leu 183) than those with moderate disease (33 per cent) (p < 0.018). Our data suggest an equal maternal and paternal contribution to the inheritance of asthma and an association of the homozygous variant (Leu 181/Leu 183) of the IgE receptor FcepsilonRIbeta with disease severity.