Combined liquid chromatography mass spectrometry (LC/MS) is still a rapidly developing area. The advantages and limitations of the most important interfaces, i.e. the moving belt interface, the thermospray interface, and continuous-flow fast atom bombardment, are discussed from a bioanalytical point of view. The discussion is underlined by two bioanalytical applications of LC/MS using a moving belt interface. The first example is the identification of unknown compounds in alkaline extracts of post-mortem human urine and plasma. The second example is actually concerned with a new approach in LC/MS: phase-system switching using a short column between the LC chromatography and the moving belt interface. The perspectives of the latter are outlined.