For further consideration of other factors except overexpansion, a review of 119 cases among 700 resections was made where small foci were palpated in the remaining lung at the time of operation and who were followed up more than one year after surgery. Copmarative studies were made regarding to incidence of postoperative complications and the rate of improvement of residual foci on these cases. Following results were obtained. 1) Reactivation occurred more frequenfly in the group of patients with cavitary disease discharging strongly positive sputum. As it was the case in incidence of postoperative complications, these factors were not considered to be predominant to reactivation. No relationship was noticed between reactivation and extent of residual lesions. 2) Incidence of reactivation and postoperative complications were different depending upon doses and duration of chemotherapy given pre and postoperatively. However, no correlation was found between improvement of residual foci and doses of chemotherapy. 3) There was found no correlation between the rate of reactivation and the duration of postoperative hospitalization. 4) The rate of reactivation was the same in both the cases who had postresectional thoracoplasty with resection of less than 4 ribs and who did not have thoracoplasty. 5) Reactivation occurred in the cases where displacement of the remaining lung was more than moderate degree, however, it was found only 18.2 per cent even in those where displacement of the lung was marked. These findings suggest of that several factors except overexpansion of the remaining lung were not definte causes of reactivation, though they might favor to its occurrence.