Oligostyrenes can effectively be analysed with respect to chemical structure and tacticity by on-line h.p.l.c./H-1 n.m.r.. The separation of the oligostyrenes into oligomers is conducted on a reversed phase column using acetonitrile as the eluent. Via on-line coupling the chromatographic peaks are directly transferred into the n.m.r. spectrometer and analysed on-flow. Information on the chemical structure of the endgroups, the degree of polymerization and the tacticity of the polymer chain is obtained. The experiments have been conducted under conditions which are common for h.p.l.c. separations, i.e. sufficiently high how rate, moderate sample concentration and on-flow detection. For the first time, the experiments have been carried out using conventional h.p.l.c.-grade acetonitrile and no deuterium lock.