2-Fluoro-4-nitrophenol-beta-D-galactopyranoside (OFPNPG) belongs to a novel class of NMR active molecules (fluoroaryl-beta-D-galactopyranosides), which are highly responsive to the action of beta-galactosidase (beta-gal). OFPNPG has a single 19F peak (-55 ppm relative to aqueous sodium trifluoroacetate). Upon cleavage by beta-gal, the pH sensitive aglycone 2-fluoro-4-nitrophenol (OFPNP) is observed at a chemical shift of -59 to -61 ppm. The chemical shift response is sufficient to observe beta-gal activity using chemical shift imaging (CSI). 19F CSI studies of enzyme activity and lacZ gene expression in 9L-glioma and MCF7 breast cancer cells are presented, providing further evidence for the utility of OFPNPG as a gene-reporter molecule for future in vivo studies.