The literature and status of knowledge concerning olfaction in birds is reviewed, and the general anatomical plan of the avian olfactory chamber is discussed. Birds that show olfactory ability through the possession and utilization of well-developed olfactory equipment, or are suspect of olfactory perception because of behavioral patterns or olfactory equipment are discussed. These are: (1) the kiwi (Apteryx) of New Zealand, (2) procellariiform birds, such as albatrosses, shearwaters, and petrels, (3) the cathartine vultures, particularly the turkey vulture (Cathartes aura), (4) the oilbird (Steatornis caripensis) of the island of Trinidad, and northern South America, and (5) the honey guides of the family Indicatoridae. Some new data suggesting a well-developed sense of smell in the honey guides (Indicatoridae) are also presented.