A method and system for providing improved drug treatment to selected animals in a retained group. Through the use of a computer system, an operator is immediately provided with the health and drug treatment history of an animal to be treated by identifying the animal. With this information and a diagnosis of the animal's health condition, a drug treatment is chosen. The diagnosis and treatment are entered into the computer system to update the animal's health and treatment history. If a drug treatment has a withdrawal time which requires the animal to remain in the group for a time after treatment, a release date is calculated. If a dosage of a drug treatment is weight-dependent, the weight of the animal is obtained and the proper dosage for the animal is calculated.