Arbuscular mycorrhizal fungi (AMF) are obligate symbionts which can only be propagated in association with intact plants or root explants. Molecular study of these fungi has been hampered by the inability to grow them in vitro and to obtain protoplasts. With the advent of advanced gene transformation systems, the opportunity has arisen to use biolistic technology to introduce foreign DNA linked to molecular markers into these fungi. The biolistic transformation system chosen for the AMF was GUS-based as this system was shown to work effectively for ectomycorrhiza. In this study the plasmid pNOM102 was used for transformation of Gigaspora rosea and transient GUS gene expression was detected in 40–50% of spores by colorimetric and immunological based methodologies.