There is little recent factual data published relating to the effectiveness of grand rounds as a forum for teaching and learning. This study, undertaken to evaluate the educational value of grand rounds at the Auckland Hospital showed that when required to answer a questionnaire based on medical information transmitted at the previous week's grand round, members of the audience who had been present scored significantly higher than those who were absent. (Possible score 16; score for those present was 12.1, those absent 3.9, p less than 0.001.) However, it was also shown that some in the audience had acquired erroneous information, and although the problem was not a large one, it is recommended that chairmen of grand rounds learn to recognise the potential for confusion when experts speak imprecisely or disagree over points of patient management.