Air pollution, especially of ground level O3, remains poorly understood and undocumented in Tanzania. The coastal city of Dar es Salaam has a population of approximately 4.4 million , and the city is one of the fast- est growing in Africa. The traffic density growth rate is 6.3% annually. However, the traffic growth rate greatly exceeds the development of a road network, which has resulted in severe traffic congestion. To our knowledge, there is no continuous study on ozone and nitrogen oxide in Tanzania. In this study, we present and discuss ozone and nitrogen oxide concentrations in the city of Dar es Salaam and the Bagamoyo Pwani region of Tanzania, east Africa.