Traffic noise levels in most cities of the world are higher than the recommended levels. Exposure to high levels of noise may cause adverse health effects such as ischemic heart diseases and noise induced hearing loss. We conducted a cross-sectional study to determine road traffic noise levels at 60 selected locations in the city of Colombo, Sri Lanka. On randomly selected days we measured equivalent continuous sound pressure level (LAeq) for six hours during the day. From these measurements LAeq for eight hours were calculated and used as the average noise level of a particular location. LAeq (8 hrs) within Colombo ranged 76.6 to 84.0 dB; well above the Sri Lankan recommendation of 63.0 dB (an increase of 13.3 to 21.0 dB), and the WHO recommendation of 55.0 dB (an increase of 21.6 to 29.0 dB). These levels translate into increase of sound pressure level by 21.4 to 794.3 times above the recommendations on the logarithmic scale of dB. Thirty-eight of 60 locations recorded levels more than 80.0 dB. Road traffic noise levels in Colombo were well above the recommended levels. Though the increase in measured decibels might not appear to be too high, in reality this translates into an increase manifold times in the sound pressure level that reaches the ear.