Since its original publication, the DynaFit software package [Kuzmic, P. (1996). Program DYNAFIT for the analysis of enzyme kinetic data: Application to HIV proteinase. Anal. Biochem. 237, 260-273] has been used in more than 500 published studies. Most applications have been in biochemistry, especially in enzyme kinetics. This paper describes a number of recently added features and capabilities, in the hope that the tool will continue to be useful to the enzymological community. Fully functional DynaFit continues to be freely available to all academic researchers from http://www.biokin.com.