Protein in white clover (Trifolium repens L.) is poorly utilised by ruminants because of its extensive degradation to ammonia in the rumen. However, white clover produces condensed tannins (CT) in its flowers, which can reduce rumen proteolysis. Effects of increasing proportions of clover dry matter (DM) as flowers (and therefore floral CT) on soluble protein, ammonia and volatile fatty acid (VFA) concentrations were determined with in vitro incubations. Minced mixtures of 0, 250, 500, 750 and 1000g/kg of DM as white clover flower (F) with the remainder as white clover leaf, were incubated in vitro and sampled after 0, 2, 4, 8, 12 and 24h. Treatments contained 0, 13, 26, 39 and 52g CT/kg DM, respectively. A further treatment with 500g/kg DM as flower and 500g/kg DM as leaf had polyethylene glycol added to remove effects of CT. Increasing the proportion of white clover as flowers from 0 to 1000g/kg DM reduced net conversion of plant N to ammonia N from 290 to 120mM/M at least partly due to reduced solubility of the protein. Treatments with 750g/kg DM or more as clover flowers reduced ammonia concentrations to levels likely to limit microbial growth. Total VFA production was not affected by flower content, although the proportion of acetate to propionate increased. The contribution of CT to treatment effects was small compared to effects attributed to difference in chemical composition between flowers and leaves.