The paper attempts to provide an outline account of the development and context of scientific and technical communication during the twentieth century. The main channels and forms of communication are reviewed, and their changing contributions to the overall pattern of information flow. The ever-increasing volume and diversity of scientific and technical information are emphasised. The paper concludes with some reflections on what may be learnt from this history.In science, by a fiction as remarkable as any to be found in law, what has once been published, even though it be in the Russian language, is spoken of as known, and it is too often forgotten that the rediscovery in the library may be a more difficult and uncertain process than the first discovery in the laboratory.So Lord Rayleigh told the British Association for the Advancement of Science in 1884 [1]. Ten years later, H.E. Armstrong was telling the Chemical Society of London that 'chemical literature is fast becoming unmanageable and uncontrollable from its very vastness. Not only is the number of papers increasing from year to year, but new journals are constantly being established. Something must be done in order to assist chemists to remain in touch with their subject and to retain their hold on the literature generally' [2]. Such complaints were far from new. In 1807 we find Thomas Young surveying the scene: 'When we contemplate the astonishing magnitude [of the literature] in any department of science … there is the greatest reason to apprehend that, from the continual multiplication of new essays which are merely repetitions of others that have been forgotten, the sciences will shortly be overwhelmed by their own unwieldy bulk' [3].During the nineteenth century there were published about two million scientific and technical papers [4], together with the scientific texts (perhaps 10% or 20% of the total) among the six million books published in that century [5]. During the twentieth century (depending on what growth rate is assumed) there were published in science and technology perhaps 100 or even 200 million papers, and many millions of books. Scientific information and its problems, both subjective and objective, loom ever larger.'In 1896', Bernal reckoned, 'there were perhaps in the world some 50,000 people who between them carried on the whole tradition of science, not more than 15,000 of whom were responsible for advancing knowledge by research ' [6]. Probably this estimate did not include industrial scientists -Reily [7] suggested that there were 100,000 scientists and engineers in 1900. In 1990, according to the