The flavonol glycosides from Bupleurum flavum Forsk., Apiaceae, are separated isocratically and identified by LC-MS. The obtained results revealed the presence of quercetin-dirhamnoside, quercetin-3-rhamnosylglucoside, quercetin-3-glucoside, iso-rhamnetin-3-rhamnosylglucoside, kaempferol-dirhamnoside, kaempferol-3-glucoside. The RP-HPLC behaviour of the flavonol glycosides is tested on Supersphere RP18, 4 mm and Hypersil ODS, 5 mm packing materials sequentially varying the composition of the aqueous/methanol mobile phase. To improve of the separation the effect of small amount of butanol isomers - iso-BuOH, sec-BuOH, n-BuOH and t-BuOH - in the eluent is examined also and the influence of the buffer system. Further, the relationship between the capacity factors log k' obtained in the RP-HPLC system for the plant extracted glycosides and the lipophilicity parameters CLOGP calculated for n-octanol-water system by the computer program ACD/logP is studied. Good correlations are established. The results indicate that the increasing of the content of tret-BuOH leads to higher values of the regression coefficient R and the same is valid for the buffer concentration. One may conclude that the RP-HPLC system with higher contents of t-BuOH and buffer imitates well the partition behavior of the glycosides in the n-octanol-water system. In the present study the best result is found for the composition of 70% buffer and 7% t-BuOH.