The influence of solvent concentration, pH, temperature, sampler solid ratio, and extraction time on the extractability of total phenolics and antioxidants from hop was investigated. The mechanism of extraction is confirmed to occur in the following steps: first, the dissolution of the phenolic compounds near the particle surface (washing), and second, the diffusion from the solid particles to the bulk of the liquid extract (slow extraction). The process is described mathematically using two concepts of the unsteady diffusion through plant material and Ponomaryov's empirical equation. The data obtained are used to establish the kinetics and thermodynamics of the extraction process.