<p>While hospital beds are at the heart of healthcare delivery, they have received little conceptual attention within the socialsciences. Instead, the focus has tended to be on explaining their changing numerical characteristics and the consequences of this for patient care, health systems functioning and the practices of the healthcare professions. While the number of beds iscertainly of critical importance, this paper pushes beyond this to examine the work that these numbers do and perform. In sodoing, it argues that beds are best thought of as a barometer in both a material and fi gurative sense. As such, beds can gauge system pressure, they act as ‘sentinel’ or warning devices should this change and are responsive to the viscosity (or flow) of health systems. And, in a figurative sense, they are refl ective of shifts in prevailing public or political opinion, as well aseconomic or biomedical trends. Beds are therefore woven into a tight web of system inter relationships and interdependencies which makes the calculation of any ‘optimum’ number of beds, either now or in the future, fraught with challenge.</p>