This paper presents an overview of the M3 (multi-biometric,multi-device and multilingual) Corpus. M3 aims to support research in multi-biometric technologies for pervasive computing using mobile devices. The corpus includes three biometrics – facial images, speech and fingerprints; three devices – the desktop PC with plug-in microphone and webcam, Pocket PC and 3G phone; as well as three languages of geographical relevance in Hong Kong –Cantonese,Putonghua and English. The multimodal user interface can readily extend from desktop computers to mobile hand helds and smart phones which have small form factors. Multimodal biometric authentication can also leverage the mutual complementarity among modalities,which is particularly useful in dynamic environmental conditions encountered in pervasive computing. For example, we should emphasize facial images over speech when verification is performed in noisy acoustic environments. M3 is designed to include variable environmental factors indoors and outdoors, simultaneous recordings across multiple devices to support comparative and contrastive investigations, bilingual text prompts to elicit both application-oriented and cognitive speech data, as well as multi-session data from a fairly large set of subjects.