The authors report their results on E.S.R. variations within the first month post-surgery in 38 traumatologic and orthopaedic patients, to evaluate the time of normalization and its attendibility in case of infection. Normalization was found within the first month postoperatively, without significant differences between orthopaedic and traumatologic patients. They think that the E.S.R. becomes significant on the control of postoperative subacute infection after the third postoperative day and propose E.S.R. evaluation after this period.