Interaction between cucurbit[8]urils and ofloxacin, fleroxacin, gatifloxacin and sparfloxacin was detected by UV and fluorometric analysis in details. The experimental results revealed that the acidity of the medium effected the interaction of the title systems. The cucurbit[8]urils could interact with ofloxacin, fleroxacin and gatifloxacin with a ratio of 1 : 1 and with sparfloxacin with a ratio of 2 : 1 when pH < 8.0. Inclusion stability constants of the systems of Q[8] with the guests detected at different pH values were 10(3)-10(4) L x mol(-1), while for SPFX it was 10(11) L2 x mol(-2). The results of the analysis of the four systems showed that the linear relation can reach 2 or 3 orders of magnitude and the limit of detection can be as low as 10(-9)-10(-7) mol x L(-1).