Background: Asthma and allergic diseases have increased in the developed countries. It is important to determine whether the same trends are occurring in the developing countries in Africa. We aimed to determine the time trend in the prevalence of exercise-induced bronchospasm (EIB) and atopic sensitisation over a ten-year period in Ghanaian schoolchildren. Methods and Findings: Two surveys conducted using the same methodology ten years apart (1993 and 2003) among schoolchildren aged 9-16 years attending urban rich (UR), urban poor (UP), and rural (R) schools. Exercise provocation consisted of free running for six minutes. Children were skin tested to mite, cat, and dog allergen. 1,095 children were exercised in 1993 and 1,848 in 2003; 916 were skin tested in 1993 and 1,861 in 2003. The prevalence of EIB increased from 3.1% (95% CI 2.2%-4.3%) to 5.2% (4.3%-6.3%); absolute percentage increase 2.1% (95% CI 0.6%-3.5%, p <0.01); among UR, UP, and R children EIB had approximately doubled from 4.2%, 1.4%, and 2.2% to 8.3%, 3.0% and 3.9% respectively. The prevalence of sensitisation had also doubled from 10.6%, 4.7%, and 4.4% to 20.2%, 10.3%, and 9.9% (UR, UP, and R respectively). Mite sensitisation remained unchanged (5.6% versus 6.4%), but sensitisation to cat and dog increased considerably from 0.7% and 0.3% to 4.6% and 3.1%, respectively. In the multiple logistic regression analysis, sensitisation (odds ratio [OR] 1.77, 95% CI 1.12-2.81), age (OR 0.88, 95% CI 0.79-0.98), school (the risk being was significantly lower in UP and R schools: OR 0.40, 95% CI 0.23-0.68 and OR 0.54, 95% CI 0.34-0.86, respectively) and year of the study (OR 1.73, 95% CI 1.13-2.66) remained significant and independent associates of EIB. Conclusions: The prevalence of both EIB and sensitisation has approximately doubled over the ten-year period amongst 9- to 16-year-old Ghanaian children irrespective of location, with both EIB and atopy being more common among the UR than the UP and R children. © 2007 Addo-Yobo et al.