Larkin - A Software Package for the Numerical Simulation of LARge Systems Arising in Chemical Reaction KINetics. Chemical reaction kinetics is one of the most important fields of applications where stiff ordinary differential equations occur. In fact, even the term ‘stiff’ originated from chemical kinetics -see CURTISS and HIRSCHFELDER [4.1], who suggested the use of backward differentiation formulae (BDF). These formulae have been selected by GEAR [4.2] in 1971 for his famous implicit multistep code DIFSUB. In order to facilitate the application of this stiff integrator, DIFSUB was later combined with certain chemical kinetics packages such as BELLCHEM due to EDELSON [4.3], HAVCHM due to STABLER and CHESICK [4.4], or KINRATE due to EDSBERG and UHLEN [4.5]. A further important progress was the development of the code called GEAR due to HINDMARSH [4.6]. That code was also (essentially) implemented in the systems FACSIMILE (see CURTIS [4.7]) and MACKSIM due to CARVER and BOYD [4.8].