The use of a microphone array for hands-free continuous speech recognition in noisy and reverberant environment is investigated. An array of four omnidirectional microphones is placed at 1.5 m distance from the talker; given the array signals, a Time Delay Compensation (TDC) module provides a beamformed signal, that is shown effective as input to a Hidden Markov Model (HMM) based recognizer. Given a small amount of sentences collected from a new speaker in a real environment, HMM adaptation further improves recognition rate. These results are confirmed both by experiments conducted in a noisy office environment and by simulations. In the latter case, different SNR and reverberation conditions were recreated by using the image method to reproduce synthetic array microphone signals.