This study investigates the effects of the main characteristics of the working condition on the vibration exposure on fork-lift trucks. Four hundred and eighty recordings were made on five trucks equipped with four different types of tyres and a ‘normal’ or an ‘anti-vibration’ seat, driven while empty or loaded, on a smooth or a rough track by three workers. An analysis of variance was performed to study the main effects and the significant interactions between these factors. A mathematical model is proposed for the weighted acceleration on the floor and on the seat in the vertical axis. This shows quantitatively that the vibration exposure is mainly influenced by the roughness of the track, the speed and the quality of the seat. Inflated tyres are preferable when an anti-vibration seat with a very low resonance frequency is used. In other cases, cushion tyres are more indicated.