In recent years the concern about the behaviour of oxidesof nitrogen (NO_x: NO, NO₂) in atmospherehas increased considerably. NO_x undergoesvarious complex atmospheric reactions to generatesecondary pollutants which are known to cause severeadverse effects on human health. This work focuses onthe study of physical and chemical fate of NO_xreleased in the atmosphere from vehicles, which arethe main sources of atmospheric NO_x.Keeping the objective and standard guidelines formonitoring in view, two typical sites near the roadwith high vehicular density were chosen for the study.One site was a relatively cleaner area with onlyvehicles as major source of pollution, and the secondsite was a traffic junction in an industrial region,where pollution levels are amongst the highest inMumbai. Ambient monitoring of NO_x was done for 24 hr continuously using chemiluminescent NO_xanalyser. The data was used to analyse temporal andspatial variation of NO, NO₂ and NO_x andtheir atmospheric chemical reactions.The monitoring results show that at larger distancefrom the road the level of NO decreases but theconcentration of NO₂ which is very harmfulremains the same. Statistical analysis is conductedto establish the relationship between likely change inNO₂ concentration as a result of NO_xemission changes.