Bulk precipitation and streamflow were sampled weekly for 77 weeks in a 54-ha upland peat catchment in Mid-Wales, and seven water quality variables were determined for each sample; specific conductivity and pH, and calcium, magnesium, sodium, potassium and chloride concentrations. Precipitation quality proved to be highly variable from week to week with occasional levels up to ten times the mean value for the period. A seasonal variation in quality was noted, all the variables except Ca 2+ and pH having peak levels in February with below-average values in the months June to October. An attempt was made to relate the variability in solute levels in precipitation to the prevailing meteorological situation in the sample week, characterised by synoptic indices and on-site meteorological data. This met with limited success except in supporting the idea of a terrestrial source for Ca 2+, suggested by cross-correlation of the quality variables and by a comparison of the elemental proportions of the samples with those of seawater. Mean solute concentrations in streamwater were higher than in precipitation in every case except for Ca 2+ though occasionally individual precipitation samples had higher concentrations than the contemporaneous streamwater samples. Solute rating curves were of very low statistical significance but instead streamwater solute concentrations were more closely related to solute concentration in the previous week's rainfall. Budget calculations show that Mg 2+, Na +, K + and Cl − in bulk precipitation account for 51, 62, 63 and 56%, respectively, of the total element output from the catchment in streamflow.