The purpose of this study was to investigate the effect of three techniques for administering subcutaneous low-dose heparin on the formation of bruises at the injection site in adult postoperative cardiothoracic surgery patients. Forty-three subjects comprised the sample. All received subcutaneous injections of heparin, 5,000 units every 12 hours postsurgery. Three subcutaneous injection techniques, identified to study the variables of needle manipulation and tracking of the medication, were administered randomly to each subject. Forty-eight hours after the third injection, the sites were observed and bruises, if present, were measured. Data were analyzed by means of the Friedman test, and a 0.569 level of significance was obtained. It was concluded that, for this sample, none of the three techniques appeared clearly superior in yielding smaller or fewer bruises.