A study of automobile pollution in Kolkata has been made using CALINE 4 model. This model was selected as it offered several advantages over other models. It has been first used as the base model to develop the correction factors for the application of this model for the city of Kolkata, and then the modified model with the correction factors has been validated. Carbon Monoxide was chosen for the model because it is principally emitted from vehicular sources and daily background concentration data of this gas were available for a year for comparative studies.