||From the past three to four decades, ecologists and scientists have exhaustively studied the effect of increased artificial light pollution at night on the ecological and physiological behavior of mammals. The Suprachiasmatic Nuclei (SCN) or master clock in the brain of mammals including humans synchronizes the physiological functions with the light: dark cycle. The prolongation of light period in the light: dark cycle disrupts the circadian rhythm of mammals causing several negative or modified physiological consequences. Changed physiological level of melatonin, an important endocrine hormone, had been identified as an important factor causing different consequences such as cancer, diabetes mellitus, metabolic disturbances, oxidative stress, and depression. The presence of artificial light at night is the demand of the era but thoughts must be given to the prevention of consequences due to artificial light pollution and ‘how much is needed’. The review paper discusses the effect of artificial light pollution on the biological clock of humans and associated negative physiological consequences. Further, the paper also briefly discusses the economics of light pollution and measures needed to prevent physiological disorders in humans.