The binding of 125I-epidermal growth factor (EGF) to the plasma membranes of 54 samples of human lung tumors was determined. These included 34 squamous cell carcinomas and 20 adenocarcinomas. Twenty samples of histologically normal lung excised surgically along with the tumors were used as controls. Most of the plasma membranes showed an EGF receptor level higher than that of normal tissue. A moderate increase in the amount of 125I-EGF bound (2-5 fold) was observed in the majority of the tumors. Only a few cases (5-10% of the total) showed a large increase (> than 10 fold). The binding of 125I-EGF was compared with clinical stages and grades of differentiation. No correlation between the stage of the tumor and 125I-EGF binding was observed. However, the highest levels of EGF receptor (EGF-R) were found in poorly differentiated squamous cell carcinomas. The total amount and the distribution pattern of gangliosides and phospholipids were analyzed in individual tumors. A decrease in GD1b, GD1a and sphingomyelin and an increase in GM1 and GM3 was observed. No correlation was detected when tumors with the highest or lowest levels of gangliosides or phospholipids were compared with tumors exhibiting the highest binding of 125I-EGF.