The authors wish to congratulate Professor Walther Lamprecht, Hannover, on the occasion of his sixtieth birthday Summary:We describe an on-line multi-cplumn high performance liquid Chromatographie method for the selective clean-up and analysis of major and minor ribonucleosides in physiological fluids. Quantitative data obtained for the determination of some methylated ribonucleosides in human urines are compared with those obtained with the traditional off-line method.The on-line technique developed in our laboratory is distinguished from the off-line method by the following features:(1) Sample clean-up and analysis of the target-compounds can easily be automatized, (2) Total time of analysis, for example of urinary ribonucleosides, is decreased to 35 minutes, (3) Laborious and error-prone evaporation and redissolution Steps are avoided, (4) Reliability of the overall analytical System can be controlled with ease, (5) Small sample-volumes can be applied directly, (6) Sensitive samples can be processed very rapidly under mild conditions, (7) Results obtained with the -line and off-line-techniques compare well. Hagemeier, Kemper, Boos and Schlimme: Quantitative determination of minor ribonucleosides (5) Kleine Probenvolumina können direkt appliziert werden, (6) Empfindliche Proben können in kürzester Zeit unter schonenden Bedingungen analysiert werden, (7) Die mit der "on-line" wie mit der "off-line"-Technik erhaltenen Ergebnisse zeigen eine gute ÜbereinŜ timmung. Entwicklung einer chromatographischen Methode zur quantitativen Bestimmung seltener Ribonucleoside in physiologischen Flüssigkeiten Charakterisierung und quantitative Bestimmung von seltenen Ribonucleosiden in physiologischen Flüssig