Discharge and luminescence properties of waters feeding a ¯owstone in Lower Cave, Bristol, were measured at both three weekly and 30 minute sampling intervals within rainfall events over the period April 1994±April 1995 and July±December 1995, respectively. Results are compared with the discharge and luminescence of lower (50 . 01 ml s 71 ) discharge waters supplying ®ve stalagmites in the cave . When sampled at three weekly intervals, the ¯owstone waters exhibit a statistically signi®cant relationship between discharge and luminescence intensity (r 0 . 75), with luminescence maxima in late autumn and early winter. When compared with the stalagmite waters, the ¯owstone waters have a higher luminescence intensity at 420 nm (28+ 11 vs. 12+ 1 luminescence units) and a higher wavelength of maximum luminescence intensity (430+ 2 vs. 419+ 1 nm). The relationship between discharge and luminescence is weaker for the ¯owstone than for the fastest dripping stalagmite waters (r 0 . 75 vs. r 0 . 85), suggesting that hysteresis and other non-linear eects on the luminescent fraction in the waters may be important under higher ¯ow regimes (40 . 01 ml s 71 ) feeding ¯owstones. When 30 minute sampling results are considered, dilution and hysteresis eects can be observed in the discharge±luminescence relationship, both on an intra-event basis and over the winter as a whole. Exhaustion of organic matter within the karst groundwater system over the hydrological year may also be important. A very rapid ¯ux of luminescent organic matter in early autumn generates a non-linear, order of magnitude change in water luminescence intensity. Flowstone water luminescence properties can be interpreted as having: (1) higher concentrations of luminescent organic matter compared with stalagmites (from luminescence intensity data); (2) a greater proportion of humic acid in relation to fulvic acid (from luminescence wavelength data); (3) a more rapid response to surface rainfall events; and (4) a consequently greater proportion of non-linear responses to surface rainfall variations. These results are considered in terms of the utility of the analysis of luminescence variations in solid samples of stalagmites and ¯owstones in aiding the reconstruction of past rainfall variations, and it is suggested that stalagmites are more useful than ¯owstones.