Naturally occurring closing and chewing forces were measured in dentitions with mandibular fixture-supported bilateral distal two-unit cantilever fixed prostheses occluding with complete dentures, and the vertical bending stress in the cantilever joint of the preferred chewing side was assessed. Occlusal forces were measured using eight miniature strain gauge transducers bilaterally and symmetrically mounted in complete dentures. Occlusal forces over the entire prosthesis were registered in basic (habitual) occlusion and with a 100-microns-high premature occlusal contact on the second cantilever unit. Closing and chewing forces increased distally. The premature occlusal contact did not significantly influence the total forces over the entire dentition but increased the local forces over the second cantilever unit. The group mean maximal vertical bending stress for closing forces reached the fatigue limit for unhardened type III dental gold alloy in basic occlusion. Although the interfered occlusion resulted in a significant redistribution of forces and significantly altered the stress contributions from each cantilever unit, maximal vertical bending stress in the cantilever joint was not significantly influenced. During chewing, the fatigue limit was not reached in basic or in interfered occlusion.