Urinary proteins play a significant role as pheromones and pheromone-binders in mammalian reproduction and social behaviour. The present study was carried out to quantify the urinary proteins in five different mammalian species viz mouse, rat, rabbit, bovine and human. The results revealed that the male rodents excrete large amounts of urinary protein as compared to that of other mammals. In addition, the male mammals excrete a higher quantity of protein than do the females., suggesting the role of androgens in excretion of protein. The presence of higher concentration of urinary proteins in rodents suggests that the rodents depend more on urinary proteins for olfactory/social communication.