(19)F MRI is emerging as a new imaging technique for cell tracking. It is particularly attractive because of its potential for direct and precise cell quantification. The most important challenge towards in vivo applications is the sensitivity of the technique, i.e. the detection limit in a reasonable imaging time. Optimal sensitivity can be achieved with dedicated (19)F compounds together with specifically adapted hardware and acquisition methods. In this paper we introduce the (19)F MRI technique focusing on these key sensitivity issues and review the state-of-the-art of (19)F MRI and developments towards its clinical use. We calculate (19)F detection limits reported in preclinical cell and clinical (19)F drug studies in terms of tissue concentration in a 1 cm(3) voxel, as an alternate way to compare detection limits. We estimate that a tissue concentration of a few millimoles per litre (mM) of (19)F is required for a human study at a resolution of 1 cm(3). Key Points • Direct and precise cell quantification can be done by (19) F MRI. • (19) F MRI sensitivity is the most important parameter towards clinical application. • A number of (technical) considerations can improve sensitivity significantly. • A few millimoles per litre (mM) of (19) F per voxel is required for adequate detection.