Cities in Africa are growing fast: over 65% of the population will live in urban areas by 2060. This rapid urbanisation is drastically increasing air pollution and greenhouse gas emissions. Air pollution is already Africa’s second biggest cause of death, after HIV/AIDS. So how can African cities catalyse growth that is fast, fair and sustainable? This report looks at the potential benefits of tackling air pollution and climate change together in four cities: Cairo, Lagos, Johannesburg and Accra. Our analysis maps the health, economic and climate impacts of increasing air pollution along a “business as usual” growth path. It then contrasts this trajectory with an alternative scenario in which cities implement clean air measures as they grow, such as upgraded public transport, cleaner cookstoves, and greener industrial technology and energy. The findings suggest that similar gains could be achieved in other major cities experiencing exponential growth across Africa.