By means of a special cell assembly, the prefilter, primary absorption, self-absorption, and postfilter effects of an analyte compound upon the signal of a fluorescent probe (aniline) could be evaluated. The experimental evaluation allowed us to model a possible mechanism of response of the negative fluorescence HPLC detector described by Syang Y. Su and co-workers and to indicate possible improvements in the flow cell design. The negative fluroescence detector's response seems to be largely based upon the prefilter, primary absorption, self-absorption, and postfilter effects of the analyte.