The outstanding properties of chemically bonded phases on high-performance thin-layer chromatographic (HPTLC) plates offer a wide range of applications in environmental analysis, not only because of simple enrichment techniques on the plates. Column optimization is another valuable field of application. The theoretical background of the latter is given in a simple treatment showing that accurate data transfer from HPTLC to high-performance liquid chromatography (HPLC) is possible, especially in reversed-phase column separations. By simultaneous multi-phase sample analysis on HP plates, optimal conditions for HPLC column separations are easily found. Two-dimensional separations on HPTLC plates show, in addition to the possibilities of on-plate controlled enrichment, that TLC is often unsurpassable in environmental trace analysis in comparison with HPLC or gas chromatography. HPTLC is often not only more effective in qualitative analysis, but can also be superior in quantitative analysis when utilized to the full.