The diagnostic value of membrane glycolipid biochemistry index, the lipid-bound sialic acid (LSA) and totalsialic acid (TSA) in cerebrospinal fluid (CSF) was evaluated in 30 intracranial and 65 gastrointestinal tumors.The plasma LSA, TSA and red cell membrane sialic acid (R-SA) in were determined according to the method ofSevenmerhulm. Our results showed that the levels of LSA and TSA in CSF of intracranial tumor patients washigher than that of normal group(p<0.01). The concentration of TSA and LSA in patients with malignant gliomawas higher than that of benign meningioma patients(P<0.01). No significance was found between intracranialhalmatoma patients and normal control group for levels of membrane glycolipids (p>0.05). Results also found thatthe plasma LSA, TSA and R-SA of gastric carcinoma were significantly higher than those of control group (p<0.05);while no significant difference was found in the plasma LSA, TSA and R-SA levels between chronic gastritis,gastrohelcoma and normal control group (p>0.05). Plasma LSA, TSA and R-SA levels of gastric carcinoma patientwere significantly higher than those of chronic gastritis patients and gastrohelcoma patients(p<0.05). It was alsofound that plasma LSA, TSA and R-SA contents were significantly higher in large intestine carcinoma patientsthan in benign in stestine tumor patients (p<0.05) while no significant difference was found between intestinebenign tumor and normal control group (p>0.05). The levels of LSA, TSA and R-SA were obviously higher inthe patients with metastasis than in the ones without (p<0.05.) The membrane glycolipid biochemistry indexLSA and TSA in CSF are sensive markers for diagnosing intracranial tumors. For gastrointestinal malignanttumors the plasma LSA TSA and red blood cell membrane SA may be considered as auxiliary indicators fordiagnosis. They can be used for distinguishing benign from malignant tumors.