The modern dielectric spectrometer is capable of real time observation of changes in the dipole activity of molecular systems. This article discusses the issues involved in such measurements and their application to a range of problems. Data are presented on the use of dielectric spectroscopy to monitor the cure of thermosetting resin systems, water absorption in polymers, physical ageing in thermoplastics and film formation and coalescence in polymer latexes. The dielectric technique is coming of age and its application to a range of interesting kinetic problems is now possible.