This paper reports on the long awaited first results of the INTERPHONE study. The interview-based case-control study with 2708 glioma and 2409 meningioma cases and matched controls was conducted in 13 countries using a common protocol, including substantial numbers of subjects who had used mobile phones for >=10 years. Thorough sensitivity analyses were conducted to strengthen the interpretation of the study. Overall, no increase in risk of either glioma or meningioma was observed in association with use of mobile phones. There were suggestions of an increased risk of glioma, and much less so meningioma, at the highest exposure levels, for ipsilateral exposures and, for glioma, for tumours in the temporal lobe. However, biases and errors prevent a causal interpretation. The possible effects of long-term heavy use of mobile phones require further investigation.