A three-pin skull clamp [10] includes a C-shaped frame [12] which partially encircles the head [18] of the patient, with a spring-loaded single skull pin assembly [22] located at one end of the frame [12] and adapted to engage the head [18] of the patient with a desired engagement force, and two spaced skull pins [30] mounted to a rocker arm [44] located at an opposite end of the frame [12]. Each of the rocker arm skull pins [30] resides in operative contact with an indicator cap [66] held by a spring-loaded pin carrier assembly [50], the indicator cap [66] being movable relative to the rest of the pin carrier assembly [50] in response to the engagement force applied to the corresponding skull pin [30] by the head [18] of the patient. By visibly comparing the positions of the indicator caps [66] relative to their respective pin carrier assemblies [50], one can readily determine whether the engagement forces are equally distributed between the two rocker arm skull pins [30]. If the indicator caps [66] show significantly unequal load distribution, the rocker arm [44] can be pivotally adjusted to produce a rocker arm orientation which results in a more equal load distribution on the two spaced rocker arm skull pins [30].