Upon administration of irinotecan(CPT-11), cholinergic symptoms, such as perspiration and abdominal pain, may develop. These symptoms are reported to increase with higher doses of CPT-11. However, to date, in Japan, factors influencing cholinergic symptoms, such as dosage of CPT-11, regular medications, and laboratory values indicating liver function, have not been studied. Therefore, to assess such factors, we conducted a retrospective investigation. Cholinergic symptoms occurred in 74(40.4%)of 183 patients. Moreover, of these 74 patients, cholinergic symptoms occurred in 45 patients(60.8%)in the first course, and sweating was the most common symptom in these patients. According to binomial logistic regression analysis, the most significant factor affecting cholinergic symptom expression was a single dose(per body surface area)(odds ratio: 1.03, 95% confidence interval: 1.02-1.05, p<0.01), and the cut-off value in the receiver operating characteristic curve was 137mg/m2. By detecting cholinergic symptoms at an early stage after the administration of a single dose of CPT-11, the discontinuation of therapy administration can be avoided, and cholinergic symptoms can be alleviated.