Pesticides are used as a means to protect plants and preserve human health. Their uncontrolled use has caused the accumulation of residues and degradation products in the environment, which negatively affects the entire ecosystem and poses a health risk to humans. Human exposure to such substances is tracked by biological monitoring. Indicators of biochemical exposure provide information on the external/absorbed dose and the toxic effects of the compound and are used for risk assessments. The essential precondition for this are reliable analytical procedures. The aim of this thesis was to propose a method for monitoring pesticide levels of imidacloprid and its metabolites, 6-chloronicotinic acid and imidacloprid urea, in biological material, i.e. urine, during long-term exposure to low doses. Procedures for accumulating these compounds from urine samples were studied using solid phase extraction on: poly(divinylbenzene-co-N-vinylpyrrolidone) (Oasis HLB), styrene-divinylbenzene (SDB-1) and octadecylsilic dioxide in combination with styrene-divinylbenzene (SDB/C18). Sample preparation was optimized for final high-performance liquid chromatography with UV diode array detector analysis. Extraction recoveries of imidacloprid and its metabolites from the Oasis HLB sorbent were within the range of (98 – 104) %, on SDB-1 (68 – 102) % and on SDB/C18 (77 – 100) %. Extraction of compounds from urine on Oasis HLB was not possible due to the inability to remove interfering polar matrices of urine. The results of extraction on SDB sorbent indicate its lack of selectivity. The extraction of compounds from urine on column SDB/C18, rinsing with a 1 % methanol in deionized water and eluting with a 20 % dichloromethane in acetonitrile, was shown to be the most suitable sample preparation procedure for final analysis using liquid chromatography. The extraction efficiency for imidacloprid and imidacloprid urea was 95 % and 91 %, (R.S.D., 7 – 12 %). 6 – chloronicotinic acid cannot be determined by extraction on the SDB/C18 column coupled with HPLC analysis. The limit of detection for both compounds was 20 ng/ml. Extraction of imidacloprid and its metabolite imidacloprid urea from urine on SDB/C18 sorbent with final HPLC – UV DAD analysis is suggested for use in assessing human exposure to imidacloprid.