Background: To assess the frequency and severity of gastrointestinal adverse effects in advanced colorectal carcinoma patients treated with four different schedules of FOLFOX. Materials and Methods: Patients (median age 61 years) who underwent surgery were included in the study. All had measureable disease at CT scan, ultrasonography or clinical examination. Toxicity was graded on a scale of 1-5 according to the general grade definition of CTC v2.0. The severity of adverse effects (Grade 3 and 4) assessed in each treatment arm was compared. Results: Differences between the incidence rates of 3 and 4 toxicity and all grades of toxicity for all parameters in GI toxicity were very highly significant (p<0.001). Severe gastrointestinal symptoms of toxicity were noted with FOLFOX7 (oxaliplatin $130mg/m^2$). Grade 3 diarrhea was reported in 25% patients and grade 4 diarrhea in 4% in the FOLFOX7 treatment arm. Grade 2 vomiting was very frequently reported in the FOLFOX4 treatment arm (oxaliplatin $85mg/m^2$). Grade 2 stomatitis was reported in 42% patients treated with mFOLFOX6 (oxaliplatin $100mg/m^2$). Differences in the incidence rate of nausea, diarrhea and stomatitis among all treatment arms of FOLFOX were significant (p<0.05). Conclusions: Severe diarrhea is associated with FOLFOX7 treatment. No grade 3 or 4 GI toxicity was reported in patients of the mFOLFOX6 arm.