Mechanical signals are major regulators of skeletal homeostasis as the addition of exogenous load is followed by enhanced bone formation and the removal of normal loads is followed by net bone loss. The mechanism by which bone cells perceive and respond to changes in their biophysical environment are still poorly understood, but it is widely accepted that the detection of interstitial fluid flow is an initiating cue. In this chapter, we describe two in vitro systems designed to examine the effects of fluid flow on bone cell behavior and to elucidate the signaling cascades activated by this stimulus. The first utilizes a parallel plate flow chamber designed to stimulate a single bone cell type grown on glass slides. The second employs a rotating disk fluid flow apparatus. Commercially-available cell culture inserts allow one type of bone cell to be exposed to fluid flow and signals to be communicated to a second bone cell model not exposed to fluid flow.