Quantitative microbiological methods are aimed at counting the number of microorganisms in a sample. They are extremely important in the pharmaceutical industry to ensure drug safety: indeed, bacteria and toxins produced by microorganisms could contaminate medicines, which may harm humans if the contamination remains undetected. Many new technologies are being developed to measure the microbial content in a sample: they are generally called rapid methods because they provide much quicker results than compendial methods, which are standardized methods and need up to 14 days to produce a result. Rapid methods need to be validated before being practically used and accuracy is one of the parameters which needs to be evaluated during validation.