The most widely used antibiotic susceptibility testing methods in Clinical Microbiology are based on the phenotypic detection of antibiotic resistance by measuring bacterial growth in the presence of the antibiotic being tested. These conventional methods take typically 24hours to obtain results. A review is presented here of recently developed techniques for the rapid determination of antibiotic susceptibility. Data obtained with different methods such as molecular techniques, flow cytometry, chemiluminescence, mass spectrometry, commercial methods used in routine work, colorimetric methods, nephelometry, microarrays, microfluids, and methods based on cell disruption and sequencing, are analyzed and discussed in detail.