Fluorimetric cell-based sensing methods have attracted increasing interest in toxicity testing of pharmaceuticals, pathogens, environmental pollutants, and other chemicals. The objective of this review is to summarise the variety of approaches reported up to now and to present recent developments in this area. The different approaches are described in relation to their underlying mechanism and, especially, to the role of the fluorophore involved. The methods discussed include the use of fluorescent or fluorogenic indicators, fluorescence-based testing for membrane integrity, approaches based on fluorescence labelling, inducible fluorescent protein expression, and analysis of cellular autofluorescence. Several of these approaches have been shown to be advantageous in comparison with non-fluorescence methods and have potential in high-throughput screening, for example in drug discovery and safety pharmacology.