<正> In this report

purified Ricinus communis agglutinin （RCAl） was employed for analysis ofoligosaccharide molecules in serum of patients with lung cancer or benign diseases.By meansof DEAE-Sephadex A-50 and Sephadex G-100 chromatography

RCAl was purified from the ex-tracts of castor beans.After characterizing its bioactivity by means of red blood coagglutination andpurification by SDS-PAGE

RCAl was coupled with CNBr-activated Sepharose 4B.By RCAl af-finity chromatography

the gtycoproteins containing Galβl-4GlcNAc-linked unit at the nonreducingend of the carbohydrate chain were isolated from the gastric cancer tissue.By means of RCAl andthis glycoproteins labelled with horseradish peroxidase

a competitive binding assay was establishedand employed to detect the level of the oligosaccharides defined by RCAl in serum of pateins withlung cancer or benign diseases and of normal persons.The results suggest that expression of theseoligosaccharide molecules is higher in serum of patient with lung cancer than in serum of patientwith a benign disease of the respiratory system and healthy individuals.The positive rates were60.6%（20/33） in serum of patients with lung cancer

21.4% （6/28） with benign diseases and 4.0%（1/25） of normal persons.It is confirmed that detection of these oligosaccharide molecules in serumcan be helpful in the study and diagnosis of lung cancer.