Abstract A review of research on the effects of classroom observers upon both teachers and pupils indicates that while effects upon the behaviour and performance of the children are noted, they are more commonly ignored, while the observer effects upon their teachers receive far greater attention. Strategies adopted by researchers, such as Hargreaves (1967), Lacey (1970) and Nash (1973), to obtain credibility in the eyes of the teachers being observed are discussed together with those adopted by the teachers themselves in order to cope with an observer's presence in the classroom, and the question is raised of the observer's credibility in the eyes of the children. Following the continuous observation of one class of 24 twelve‐year‐old children with 12 of their teachers over a five‐week period by the author, the suggestion is made that children react to an observer's presence in ways which relate more to the researcher's personality than to him as an object. Evidence obtained from observation and from dis...