Phenolic compounds in the fruit of American cranberry (Vaccinium macrocarpon Aiton) determine the antioxidant, anti-inflammatory, anticancer, and other biological effects. The berries are used in the production of medicinal preparations and food supplements, which highlights the importance of qualitative and quantitative analysis of phenolic compounds in cranberry fruit raw material. The aim of our study was to develop and validate an efficient, cost-effective, reproducible, and fast UPLC-DAD methodology for the evaluation of the qualitative and quantitative composition of phenolic compounds in raw material and preparations of American cranberry fruit. During the development of the methodology, chlorogenic acid and the following flavonols were identified in cranberry fruit samples: myricetin-3-galactoside, quercetin-3-galactoside, quercetin-3-glucoside, quercetin-3-a-L-arabinopyranoside, quercetin-3-a-L-arabinofuranoside, quercetin-3-rhamnoside, myricetin, and quercetin. The developed and optimized UPLC-DAD methodology was validated according to the guidelines of the International Council for Harmonization (ICH), evaluating the following parameters: range, specificity, linearity (R2 > 0.999), precision (%RSD < 2%), LOD (0.38-1.01 micro g/mL), LOQ (0.54-3.06 micro g/mL), and recovery (80-110%). The developed methodology was applied to evaluate the qualitative and quantitative composition of phenolic compounds in fruit samples of cranberry cultivars 'Baifay', 'Bergman', 'Prolific', and 'Searles', as well as 'Bain-MC' and 'BL-12' clones. In the tested samples, the majority (about 70%) of the identified flavonols were quercetin derivatives. The greatest amount of quercetin-3-galactoside (1035.35 +or- 4.26 micro g/g DW) was found in fruit samples of the 'Searles' cultivar, and the greatest amount of myricetin-3-galactoside (940.06 +or- 24.91 micro g/g DW) was detected in fruit samples of the 'Woolman' cultivar