Background : Obesity is associated with increasing risk of cancers. However chemotherapy dosing in obese patient has been reported under recommended dose according to toxicity concern. This study therefore reported the chemotherapy dose adjustment and safety outcome in obese cancer patient.Objective : To describe chemotherapy dose adjustment pattern and safety outcome in obese cancer patient at Surin hospitalStudy Design : cross-sectional studyMethods : A retrospective review of obese patient receiving chemotherapy at Surin hospital was conducted during January 1 to 31 December 2014. Patient's characteristic, ideal body weight, body surface area and adverse reaction during chemotherapy courses were collected for data analysis. Research data was analyzed and presented with percentage, mean with standard deviation. Comparative tests were paired t-test, chi-square and fisher's exact test.Results : There were 43 obese patients (7.9%) from overall 541 cancer patients receiving chemotherapy during period of this study. Obese patients were mostly female (40 cases) with average age 53.5 ? 8.2 years and average body mass index was 28.5 ? 4.3 kg/m . Breast cancer was the most prevalent among obese cancer patients (58.14%). Thirty-nine obese cancer patients received chemotherapy based on body surface area of their ideal body weight while only 4 patients received full-based weight chemotherapy dose. Relative chemotherapy dose intensity in obese patient was 0.9 ? 0.1 (p = 0.002). Serious adverse drug reactions of anemia and mucositis had been reported.Conclusion : Despite most of obese cancer patients were assigned adjusted chemotherapy dose based on their ideal body weight, the relative dose intensity was not significantly different. Few serious adverse events were observed and further efficacy outcome had been suggested.