The ‘rag-bag character of ‘coli-aerogenes’ bacteria used originally as markers for process failure has prompted their substitution by the taxonomically accurately delineated group of Enterobacteriaceae. Media previously used for the detection or enumeration of the coli-aerogenes group can be adapted to monitoring Enterobacteriaceae simply by replacing lactose by glucose. Test strains including fastidious as well as more robust Enterobacteriaceae are used for the evaluation of media considered appropriate. They should be recovered within 0.5 log10 of cfu-numbers obtained on non-selective media whereas sporeformers and cocci should lead to less than 5 log10 cycles of the recovery on or in control media.