This work is focused on application of laser-induced fluorescence detection for analysis of amino acids, peptides and proteins. The measurements were performed on a home-built instrument with a frequency-doubled Nd:YAG laser (532 nm) as excitation source. Rhodamine B isothiocyanate was used for derivatization of model samples. Major differences between the detection limits of analytes derivatized at high and low concentrations were presented. Difficulties associated with derivatization of complex samples and their negative influence on the limits of detection were also demonstrated.