Frictional vibrations, which occur when two solid bodies are rubbed together, are analyzed mathematically and observed experimentally. In the mathematical analysis, the non-linear differential equation of motion during the slip period is derived making use of the experimental friction-velocity curve. A qualitative graphical solution of this differential equation of motion is presented to illustrate the general form and behavior of the motion. The experimental friction-velocity curve is then linearized allowing the differential equation of motion to undergo standard analytical solution. The experimental investigations were carried out using unlubricated steel surfaces and six different supporting systems. The experiments were confined to sliding in the negative slope region of the friction curve for the particular surfaces used. The effects of load, stiffness and velocity of the translating surface are considered and the results suggest that the decay of the vibrations, as the speed of the moving surface is increased, corresponds in form to the friction-velocity curve for the surfaces used. Using the original analytical relationship describing the shape of the negative slope region of the friction curve, the theoretical results are altered accordingly. Good correlation is obtained between the analytical results and the experimental observations.