A process for the production of detergent particles, comprises feeding an acid precursor of an anionic surfactant and a neutralising agent into a horizontal thin-film evaporator/drier comprising a mixing region, a drying region and a cooling region. The resultant detergent particles are graded to separate an oversize granule fraction in which at least 70 wt % of the particles have a minimum diameter of 1000 &mgr;m. This fraction is fed back into the process.