Confluent biological tissues are active multicellular systems: cells consume energy (ATP) to generate motion, change shape and exert forces. Mechanical stresses are known to regulate cell proliferation, extrusion, differentiation and collective migration, so quantifying the pressure inside a tissue is a major biophysical question. Yet in out-of-equilibrium active systems the notion of pressure is subtle. Unlike in equilibrium, pressure is generally not a state function: the force exerted on a wall or probe can depend on how the active constituents interact with it (its shape, stiffness, compliance, and the nature of the contact). This implies that different pressure measurements (wall force, bulk stress, deformation of a probe) may give different answers for the same tissue. Biological cells make this problem harder than for synthetic active particles (self-propelled colloids, active Brownian particles). Cells deform, adapt and communicate; their interactions are intrinsically many-body rather than pairwise (a cell’s mechanics depends on the whole polygon formed with its neighbors); and the direction of cell motility is coupled to cell geometry and/or to the orientation of neighboring cells. How these features affect the pressure exerted on a confining wall is largely unexplored.