Researchers are often confronted with problems requiring consideration of a large number of factors. Because such situations require large and costly experimental programs, an efficient method of factor screening is often needed. This article examines the performance characteristics of two-stage group screening experiments. To evaluate performance, random grouping and a constant signal-to-noise ratio for all active effects are assumed. No presumption is made concerning the directions of possible effects. As part of the investigation, a computer-aided search routine is developed to provide guidance in selecting and using a satisfactory two-stage group screening strategy. Important practical considerations are also discussed.