BACKGROUND AND OBJECTIVES: Hospital pharmacists collaborate in clinical trials by managing the reception, conservation, distribution, return and destruction of the investigational medical products (IMP). However, errors can happen during the simultaneous management of multiple trials because each clinical trial stipulates its own method for managing the drug under study. In order to promote optimal management by hospital pharmacists, we developed a method for calculating a risk of error index for each experimental protocol, and wrote standard procedures for managing trials assigned low, moderate and high risk levels, to provide hospital pharmacists with a systematic tool for reducing human error in the management of IMPs for multiple clinical trials. METHODS: Calculation of this risk of error index (ρ) entails four factors: the pharmacological risk of error (φ) inherent in the pharmacological characteristics and route of administration of the IMP (carcinogenic, mutagenic, cytotoxic nature of the drug, parental or non-parenteral administration), the technological risk of error (α) involved should drug compounding be required, the risk of error related to the number of patients enrolled (n RESULTS: Calculations of this formula for 60 active trials indicated that seven (11.7%) of the protocols were low risk of hospital pharmacist error, 43 (71.7%) were moderate risk and 10 (16.6%) were high risk. For each of these categories (low, moderate and high risk) we have outlined standard procedures in order to minimise the occurrence of any errors. CONCLUSIONS: Following validation of our formula and standard procedures by the ISMETT Research Institute, we are promoting the use of the tool in other clinical centres as we believe it can help hospital pharmacists minimise the risk of error in managing experimental drugs for clinical trials.