Aims: Lenticules(TM) consist of control-dried plano convex discs in which biologically-active materials are contained within a water-soluble matrix. They can be produced to contain stable numbers of bacteria from 10 cfu lenticule(-1) to 10(8) cfu lenticule(-1) with a wide variety of, organisms. These experiments were carried, out to validate their use as a tool for internal quality control in quantitative microbiology. Methods and Results: The Lenticules(TM) were used routinely in standard quantitative microbiological procedures across five laboratories. Results showed the materials to be stable, homogenous and capable of identifying systematic errors. Conclusions: The Lenticules(TM) provide suitable, stable control materials. Significance and Impact of the Study: Routine internal quality control of quantitative measurements is greatly improved; the materials are easy to use and enable comparisons between laboratories to be made.