The prevalence of allergic diseases is reported to have increased worldwide. Two questionnaire surveys, five years apart, were conducted to evaluate the trend of prevalence rates and possible risk factors among primary school children in Ankara, Turkey. A previous survey in 1992 revealed the lifetime prevalences of asthma, wheezing, allergic rhinitis and atopic dermatitis were 17.4%, 23.3%, 28% and 6.1%, and the prevalences for the last 12 months were 8.3%, 11.9%, 15.4% and 4%, respectively. The survey was repeated with the same questionnaire in the same age group (6-13 years) of the same school in May 1997. The parents of 358 boys and 380 girls completed the questionnaire. The lifetime and last 12 months' prevalences of asthma, wheezing, rhinitis and atopic dermatitis were 16.8%, 22.5%, 18.7%, 6.5%, and 9.8%, 13.3%, 14.1%, 4.3%, respectively. There was a significant change only for the lifetime prevalence of rhinitis (p < 0.001). The rate of indoor smoking had declined from 73.9% to 64%, and pet ownership had risen from 7.9% to 22.9% (p < 0.001 for both). Atopic family history was the most prominent risk factor for all types of allergic disorders. Male gender was a significant risk factor for current asthma and wheezing [odds ratio (OR) = 1.80 and 1.59; 95% confidence intervals (CI) = 1.09-2.98 and 1.01-2.48, respectively], and passive smoking affected the occurrence of allergic rhinitis (OR = 1.84; CI = 1.13-3.00). The prevalence rates of allergic diseases among primary school children in Ankara stabilized during a 5-year period for all diseases other than allergic rhinitis. However, there are changing behavior patterns, i.e. indoor smoking and keeping pet animals, which that may have affected these rates.