Until now, the determination of the bacterial content in purified water and water for injection purposes has been based almost exclusively on time-consuming laboratory tests based on cell cultures. However, plate counting, which has been practiced for over 130 years, is an estimation of bacteria with high variability. This is based on the visual counting of a colony of cells. The pharmaceutical industry estimates that over 80% of false positives are due to human error. These off-line tests are cost- and time-intensive. Results are usually only available after many days. Latest technical developments enable accurate, timely and comprehensive measurements of contamination by microorganisms and inert particles in pharmaceutical water systems. This enables trending and faster intervention in the event of a decrease in quality. In this presentation, in addition to the legal provisions, the historically grown current state, future-oriented technology will also be taken into account.