We conducted a questionnaire survey of first graders from six elementary schools in three areas of Yokohama annually from 1986 to 1991 (about 700 children each year) to investigate the changes in prevalence of asthma-like symptoms and association with potential risk factors. The prevalence rate of asthma-like symptoms increased from 7.6% to 11.0% in boys and from 6.5% to 8.8% in girls from 1986 to 1991. The ratio of affected boys was consistently higher than that in girls, but there were no significant regional differences. We found statistically significant odds ratios for the effect of a previous history of allergies, respiratory disease before age two, wheezing or difficulty in breath before age two and cough without respiratory tract infections on the prevalence of asthma-like symptoms.