The healing of test wounds was studied in 108 patients, in whom some impairment of wound healing was suspected. A 5 cm skin wound was performed in the forearm and the strength of the wound was tested after 5 days using the technique described by Sandblom and associates with two measurements in each wound. No differences in wound strength could be registered between the two wounds in each patient, between males and females nor in patients with malignant disease compared to other patients. Patients with low serum protein or serum albumin values had significantly weaker wounds than patients with normal protein values. Patients over 80 years of age had wounds somewhat weaker than those below 70, the difference having a statistical significance of 6%. The wound strength in patients was compared to values found elsewhere for wounds in rabbits, rats, and piglets. The pigs had much higher values than others, rabbits slightly stronger than and rats about equal to humans.