This report describes the aims, discussion and outcomes of the first Human Micronucleus collaborative project workshop on the buccal micronucleus assay. It was agreed at the workshop that three activities should be initiated as soon as possible namely (i) a method for collection of databases, (ii) writing of a protocol based on the most commonly used and best validated procedures and (iii) an inter-laboratory slide-scoring exercise in this order. A follow-up workshop is planned at the 10th International Conference on Environmental Mutagens in Florence in 2009.