Educational article describing the instrumentation of turbidimetry and nephelometry. The light sources, as well as functional problems, technicians face using these methods, are discussed. A separate chapter concerns the possibilities of an antigen excess detection and thus „hook effect“ recognition on Heidelberger-Kendall curve. The survey of contemporary instrumentation in the area of nephelometry (Quick Read, Turbox Plus, Minineph, BN Pro Spec, Nephelometer II, Array 360, Array Protein System, Immage, Immage 800, Delta, Nepheloskan Ascent, NEPHELOstar) includes a brief technical description and a presentation of used immunoassay principles.

        Key words: turbidimetry, nephelometry, antigen excess, nephelometers.