In problems where guidance to the proximity of a point is required, the probable success of the mission often is described by the probability of hitting within a given radius of the point. In this paper is presented a method of determining the probability of a hit within a given circle when it is assumed that the guidance error is distributed according to a bivariate normal distribution. This problem can be solved readily if the random error variables are independently distributed along two orthogonal axes with equal standard deviations and if they are not biased relative to the target location. Since these assumptions often are not valid, a series solution to the general problem is provided with an analysis of the error introduced by considering only a finite number of the terms.