To study food disruption and bolus formation, a simulator of mastication (AM2) was developed to mimic masticatory behaviour and allow collection of a bolus at any stage in the masticatory sequence. Here we set out to validate the AM2 by comparing boluses obtained in vitro and in vivo. Boluses were obtained from the AM2 and 30 young dentate subjects chewing peanuts and carrots. Median particle sizes (d(50)) of the boluses were extracted from image analysis results. The number of cycles was set at the mean in vivo value. The force range was chosen to match in vitro and in vivo values. The AM2 proved reliable: no significant difference between repetitions was observed. The in vitro and in vivo boluses displayed the same d(50) values for each food. In vitro and in vivo boluses obtained at different times during the chewing process were also similar. (C) 2010 Elsevier Ltd. All rights reserved.