Key constraints in process innovation are the time and cost spent obtaining data to identify and verify novel processes. Businesses are under increasing pressure to deliver products in shorter times; pressure which restricts and often prevents access to innovative and intensive processing options. The Britest project has identified key decisions in process design and the associated minimum data requirements. These involve identification and manipulation of the relevant rate processes and consideration of the phases of matter that are (or could be) present. By use of qualitative and semi-quantitative reasoning it is possible to produce a range of possible process options very early in design. This is particularly useful in the low-tonnage chemicals sectors (fine and effect chemicals) where process design is primarily an empirical activity. It also helps to deal rationally with the complex chemistry prevalent in those industries. The early identification of options allows timely development of experimental programmes to evaluate the options. An illustrative example based on a diazotisation and the associated decomposition reaction is presented. © 2003 Society of Chemical Industry.