The paper describes some of the procedures for finding out whether a given component is suitably designed for incorporation in a range of radio or television receivers, and gives a survey of some of the results obtained in carrying out such tests in one particular laboratory. Many of the tests applied to components are of a straightforward routine kind, such as the measurement of capacitance, resistance or inductance of normal values by standard methods; these are not described in detail, but where a measurement is made by an unusual method or where special test machinery of general usefulness has been devised a fuller description is given.The tests come under three main headings: mechanical, electrical and chemical. Under each of these headings there are three kinds of tests: measurement, such as of mechanical or electrical dimensions; life tests, in which the component is tested in some way representative of the effects of normal use, over a period of about five years and peak-load or overload tests.