Becchi-Rouet-Stora-Tyutin quantization of superconformal theories.

We construct and apply the complex contour method to the Becchi-Rouet-Stora-Tyutin (BRST) quantization of string theories with N = 0, 1, 2, and 4 super-Virasoro algebras. Our method makes the calculations very simple. We also calculate the central charge in the BRST quantization of N = 3 super-Virasoro algebra, although a Lagrangian realization of this algebra has not yet been constructed. This is made possible by using a formulation of BRST quantization due to Fradkin and Vilkovisky. We also comment on the application of our results to the quantization of the systems with Kac-Moody constraints.