Topology control is the problem of adjusting the transmission parameters, chiefly power, of nodes in a Mobile Ad Hoc Network (MANET) to achieve a desired topology. Over the last several years, this problem has received much attention. Despite this work however, the stability of available techniques has not been studied. This paper presents the first control- theoretic investigation of topology control in MANETs. We take a simple representative fully distributed topology control algorithm called LINT and show that it is unstable under certain conditions. We then formulate LINT in a control-theoretic context, and derive a new mechanism called CLINT that is shown to be stable for a wide range of parameter variations. We compare the in- practice performance of LINT and CLINT using comprehensive simulations and show that CLINT provides a higher throughput.