This paper presents an investigation on the behaviour and strength of slab-column joints in multystorey buildings. Such joints may develop different potential failure modes such as crushing of the concrete of the slab (due to column loading), bending or punching shear failures (due to slab loading). The paper presents the results of a test series on 9 full-scale slabs (250 mm thick) loaded to simulate simultaneously column and slab loading. The ratio between the loads was varied from moderate to fairly large column loading. The experimental results confirm a strong interaction between column and slab loads with unexpected increases on the punching shear strength as column loads are larger than the uniaxial compressive strength of the slab. The observed behaviours can be explained on the basis of the theory of plasticity and by using the Critical Shear Crack Theory, leading to a physically-grounded design method for these regions.