This paper deals with the theory of monopulse angle tracking with a laser radar employing heterodyne detection. The detector is assumed to be of the quadrant type. The target's angular location is inferred from the location of its diffraction pattern in the detector plane. A generalized gain characteristic for the detector can be used to relate the strength of the matched filter outputs, which correspond to the spatial regions (halves) of the detector surface, to the corresponding angular location of the target. The maximum likelihood angle estimator is derived for a speckle target. The performance of an approximation to the maximum likelihood angle estimator is evaluated for both the speckle and glint targets. The angle estimator performance is also evaluated in the presence of atmospheric turbulence and beam jitter.