The various ways in whieh C non-invarianee could appear in eleetromagnetie interactions are reviewed and the pertinent experimental consequences are analyzed with a detailed discussion of a few typical cases.It is stressed that, even though C invariance might be badly broken, all experiments one can think of, at present, in order to observe its possible consequences, appear as searches fora measurable effect of at most a few per cent. This is due to various reasons which are indieated.