This paper describes the application of a CUSUM chart to monitor increase (shift) in the incidences of HIV/AIDS using data from Oyo state. HIV/AIDS is one of the deadly diseases in Nigeria and the world at large and many research have been carried out by different authors on the causative factors, however the need to monitor changes in the rate of infection is desirable so that factors responsible for the high number of patients testing positive to the disease can be quickly identified and urgent and necessary action taken to curb its
spread