An exact analysis is presented for investigating parallel plate-fed slot antennas loaded by a dielectric cylinder. The primary excitation is taken to be either a TM incident mode of the parallel-plate waveguide or an incident H-polarized plane wave. The analysis combines singular integral equations with separation of variables techniques. The resulting integral equations are discretized using quasi-analytical methods, which lead to computationally efficient expressions for all matrix elements. This, in conjunction with the small matrix sizes required, leads to very accurate results with low computational cost. The numerical results presented reveal the effect of the load on the characteristics of the antennas.