When tracking a target in clutter, a measurement may have originated from either the target, clutter, or some other source. The measurement with the strongest intensity (amplitude) in the neighborhood of the predicted target measurement is known as the "strongest neighbor" (SN) measurement. A simple and commonly used method for tracking in clutter is the so-called strongest neighbor filter (SNF), which uses the SN measurement at each time as if it were the true one. This paper deals with tracking in clutter with the SN measurements. It presents analytic results, along with useful comments, for the SN measurement and the SNF, including the a priori and a posteriori probabilities of data association events, the conditional probability density functions and the covariance matrices of the SN measurement, and various mean-square-error matrices of state prediction and state update. These results provide valuable insight into the problem of tracking in clutter and theoretical foundation for the development of improved tracking algorithms, for performance analysis, prediction, and comparison of tracking with the SN measurements, and for solving some important detection-tracking problems, such as the optimal determination of the detection threshold and gate size.