Many arthropods are infected with maternally transmitted, intracellular bacteria of the genus Wolbachia. These infections often produce 'cytoplasmic incompatibility' (CI)--reduced egg-hatch frequencies when uninfected females mate with infected males or when males and females carrying different Wolbachia strains mate. Because infected females often enjoy a fitness advantage--they are effectively immune to any effects from males carrying the same Wolbachia strain--Wolbachia and associated cytoplasmic elements can spread rapidly through natural populations. Wolbachia might therefore drive transgenes associated with disease control or pest abatement into populations. In this paper, simple mathematical analyses are presented of three alternative strategies for 'CI drive'. The analyses reveal which parameters must be estimated in order to predict population dynamics, and they demonstrate stringent requirements for initially driving and/or maintaining transgenes in target populations.