There are many different air quality indexes, which represent the global urban air pollution situation. Although the index proposed by USEPA gives an overall assessment of air quality, it does not include the combined effects (or synergistic effects) of the major air pollutants (Shenfeld, 1970; Ott and Thom, 1976; Thom and Ott, 1976; Murena, 2004). So an attempt is made to calculate the Air Quality Index based on Factor Analysis (NAQI) which incorporates the deficiencies of USEPA method. The daily, monthly and seasonal air quality indexes were calculated by using both these methods. It is observed that a significant difference exists between NAQI and EPAQI. However, NAQI followed the trends of EPAQI when plotted against time. Further, the indexes were used to rank various seasons in terms of air pollution. The higher index value indicates more pollution in relative terms. Moreover, the index may be used for comparing the daily and seasonal pollution levels in different sites.