OBJECTIVE: To quantify levels of exposure to cytotoxic drugs among health professionals in order to establish an exposure threshold and implement measures to increase protection and safety. MATERIAL AND METHOD: Contamination with 5-fluorouracil, gemcitabine and cyclophosphamide was measured on work surfaces in the following areas: a class II type B3 biological safety cabinet (S(1)), a treatment prep table in an antechamber (S(2)) and a desk from the administrative room in the Outpatient Unit (S(3)). We took samples from the work surfaces by wiping them with an absorbent cloth at time t(0), prior to the work session, and at t(1) after three hours of work. For each surface, we calculated the median mass value with respect to the baseline value and the 90th, 75th, 50th and 25th percentiles for each cytotoxin in µg/m(2). Distribution normality was assessed using the Shapiro-Wilk test. Statistical analysis included the Kruskal-Wallis and Mann-Whitney-Wilcoxon tests. Statistical significance was established for values of P<.05. RESULTS: We gathered a total of 90 samples, 30 from each of the studied work surfaces. The mean recorded mass of any of the cytotoxic compounds was higher for S(1) and t(1), with values of P=.017 and P=.004 respectively. The target value for each cytotoxic drug was established at the 25th percentile, where undetectable contamination values were obtained. CONCLUSIONS: Introducing a continuous programme to monitor work surfaces for an array of cytotoxic compounds is fundamental in order to establish acceptable levels of residual contamination and reduce exposure in the workplace.