The amount of nitric oxide (NO), nitrogen dioxide (NO₂) and total mono-nitrogen oxides (NO_x) in mainstream smoke is of regulatory concern, but to date few reliable methods exist for the accurate measurement of these compounds. NO can be difficult to reliability analyze since it reacts rapidly with oxygen to form NO₂ and the measurement of aged mainstream smoke will overestimate the concentration of NO₂. In order to overcome this reactivity, we will present the results from a novel and robust method for the quasi real time analysis of NO, NO₂ and total NO_x present in fresh mainstream smoke. Smoke samples were collected with an automatic 20 port rotary smoking machine interfaced with an Ecophysics chemiluminescent analyser. Gas samples were measured on a puff-by-puff basis and reported per puff and total mass per cigarette. We will present data for NO, NO₂ and total NO_x measured in 1R5F, 3R4F and CM7 mainstream smoke collected under ISO conditions over three days. A comparison of the data collected with this method will also be compared to other published results with an emphasis on smoke aging effects.