Buttocks, covered with fat, became a real problem for doctors: the matter is that many injections don`t reach the goal. To react buttock`s mussels one needs long needle, researchers noted. Needles of standard size are absolutely useless for 23 out of 25 women, whose buttocks were examined after intramuscular injection. 2/3 of patients, who participated in investigation, didn`t get whole dose of medicine because it stayed in fat tissues of buttocks. Investigations were held in Adelaida hospital, Dublin. Despite the fact that patients didn`t get subscribed medicine in necessary dose, remains of medicine, which stayed in fat tissues, can cause infections and irritations. Buttock is practically ideal place for intramuscular injections: they have the least amount of important blood vessels, nerves and bones which can be damaged by needle. From another side large amount of small blood vessels in mussels deliver medical product to other parts of body. At the same time fat tissues are lack of blood vessels. Obesity became the problem of more than 300 millions of people in the world. Index of fatness is determined as ration of height to weight: as a rule, in case of obesity this index exceeds 30. About 65% of adult Americans have excess weight or obesity.