A continuous culture system (chemostat) was used to study the post-antibiotic effect (PAE) of beta-lactams, against slowly-growing Helicobacter pylori NCTC 11637. H. pylori was grown at one quarter of its maximum specific growth rate (mu(max)) before exposure to ampicillin, amoxycillin, azlocillin, piperacillin or cefixime (8 x MIC). After 8 h, the antibiotics were inactivated. Viable counts were used to determine the rate of recovery of H. pylori. The recovery growth rate of H. pylori was similar to the maximum growth rate of H. pylori under antibiotic-free experimental conditions, so none of the beta-lactams studied showed a PAE against slowly-growing H. pylori.