Cells present in processed lipoaspirate tissue are used to treat patients. Methods of treating patients include processing adipose tissue to deliver a concentrated amount of stem cells obtained from the adipose tissue to a patient. The methods may be practiced in a closed system so that the stem cells are not exposed to an external environment prior to being administered to a patient. Compositions that are administered to a patient include a mixture of adipose tissue and stem cells so that the composition has a higher concentration of stem cells than when the adipose tissue was removed from the patient.