Three databases of HPLC retention indices in the 1-nitroalkane scale were recently established (IFM = Institute of Forensic Medicine, MCL = Microchemistry Laboratory, MTSS = Merck Tox Screening System). In two of them (IFM and MTSS) virtually identical chromatographic conditions were applied but different RP-columns. In the third system (MCL) a different column and different elution conditions were used. Among a total of 1149 drugs examined in all three labs, 258 drugs were common for IFM and MTSS, 179 were common for MCL and MTSS, 162 were common for IFM and MCL, and 135 drugs were common for all three databases.