The erythrocyte sedimentation rate and total white cell count were measured in 110 patients who underwent lumbar spine surgery. Measurements were made before surgery; at 2 and 4 days; and at 1,2,6, and 16 weeks after surgery. A rapid increase of erythrocyte sedimentation rate was seen with peak value on the fourth postoperative day. After 2 weeks, the values were normalized for the majority of patients. Maximum mean peak value was seen 4 days after surgery for fusion (ESR= 102), which was higher than after disc surgery (ESR = 75). There was no corresponding change in total white cell count. No deep infection was noted in the study group. The erythrocyte sedimentation rate values and total white blood cell count at the time of diagnosis for five patients with postoperative deep infection were used for comparison. At the time of diagnosis, all patients with deep infection had an erythrocyte sedimentation rate value exceeding the corresponding mean value (+ 2 SD). Total white cell count was slightly elevated in one of the five infected patients; the remaining four had a normal count. Erythrocyte sedimentation rate determination shows a homogenous pattern with rapid increase and decline after lumbar spinal surgery in patients without postoperative infection, and patients with postoperative deep infection at the time of diagnosis show erythrocyte sedimentation rate elevation to a degree that usually makes the result diagnostic.