Two novel continuous processes for the chemical derivatisation of starch have been developed. A gas-solid fluidized bed process for modifications with gaseous substrates and a gel process in a static mixer reactor for handling concentrated pastes. Based on results obtained with hydroxyethylation (dryprocess) and hydroxypropylation (gel-process) it can be concluded that both processes are very attractive relative to the classical slurry process with respect to improved reaction selectivity, much shorter residence times and superior controlability and safety.