['There are no studies that describe the impact of the cumulative fluid balance on the outcomes of cancer patients admitted to intensive care units ICUs. The aim of our study was to evaluate the relationship between fluid balance and clinical outcomes in these patients.', 'One hundred twenty-two cancer patients were prospectively evaluated for survival during a 30-day period. Univariate (Chi-square, t-test, Mann-Whitney) and multiple logistic regression analyses were used to identify the admission parameters associated with mortality.', 'The mean cumulative fluid balance was significantly higher in non-survivors than in survivors [1675\u2009ml/24\u2009h (471-2921) vs. 887\u2009ml/24\u2009h (104-557), P\u2009=\u20090.017]. We used the area under the curve and the intersection of the sensibility and specificity curves to define a cumulative fluid balance value of 1100\u2009ml/24\u2009h. This value was used in the univariate model. In the multivariate model, the following variables were significantly associated with mortality in cancer patients: the Acute Physiology and Chronic Health Evaluation II score at admission [Odds ratio (OR) 1.15; 95% confidence interval (CI) (1.05-1.26), P\u2009=\u20090.003], the Lung Injury Score at admission [OR 2.23; 95% CI (1.29-3.87), P\u2009=\u20090.004] and a positive fluid balance higher than 1100\u2009ml/24\u2009h at ICU [OR 5.14; 95% CI (1.45-18.24), P\u2009=\u20090.011].'] Is positive fluid balance associated with reduced survival in critically ill patients with cancer?