Relationship between prolonged life span and changes of serum IAP and albumin induced by the therapy of lentinan plus tegafur were analysed on 43 cases with inoperable and recurrent gastric cancer. Antitumor effect was observed only in one case (2%). Other clinical effects such as improvement of performance status (PS), appetite or pain were observed in 18 cases (42%). Decrease of serum IAP was observed in 25 cases (58%) and increase of albumin was observed in 20 cases (47%). The changes of these two factors seemed to be reversely correlated. Among 30 cases which didn't show decrease of albumin, we found no increase of serum-IAP in 22 cases (72%). In the cases which showed decrease of serum IAP from abnormally high level (more than 500 mu/ml) and increase of albumin from abnormally low level (less than 3.5g/dl), prolonged life span was observed by comparison with the other cases. The cases with any clinical effect contained 78% of the cases without increase of serum IAP, and 72% of the cases without decrease of albumin. These results suggested that life prolongation effect or improvement of clinical symptoms by our therapy was closely related to the change of these serum factors.