Abstract. Concentrations of ambient NH₃, NO, NO₂ and SO₂ were measured over Bay of Bengal (BoB) during 28 December 2008 to 25 January 2009 to study their diurnal variation and relationship of NH₃ with other trace gases over BoB. The measurements were done under the winter phase of Integrated Campaign on Aerosols and Radiation Budget (W_ICARB). For the first time, ambient NH₃ was monitored precisely over BoB based on chemiluminescence method, having estimation efficiency more precise than the chemical trap method. The average concentration of ambient NH₃, NO, NO₂ and SO₂ were recorded as 4.78 ± 1.68, 1.89 ± 1.26, 0.31 ± 0.14 and 0.80 ± 0.30 μg m⁻³, respectively, over BoB. The prominent latitudinal and longitudinal variations of the trace gases were observed over BoB, whereas NH₃ and NO showed the non-significant diurnal variation. Results reveal that the concentration of ambient NH₃ negatively correlated with ambient NO₂ (r² = −0.56), SO₂ (r² = −0.58) and ambient temperature (r² = −0.27) during the study.