The purpose of this paper is to review the current developments in the observation of 0.2 to 100 keV X-rays originating outside the solar system. Discussion will be limited to experiments which are presently being developed and are likely to be flown within the next three years or so. Throughout this period experimental limits will continue to be set primarily by the available launch vehicles. Small rockets, and for energies above 20 keV, steerable balloons will continue to be the principal means of observation of cosmic X-rays, though with increasing use being made throughout the period of attitude controlled rockets (see, for example, Hazell, Cope & Walker 1968). In 1970 or 1971, the first satellite payloads specifically designed for cosmic X-ray studies should be launched, bringing a notable advance in sensitivity and resolution of the observations. There have been several excellent review articles published recently describing the different techniques useful in X-ray studies (e.g. Giacconiet et al . 1968; Aitken 1968) and therefore it is the present intention to review the current situation from the viewpoint of the observational aims of cosmic X-ray astronomy. For illustration of the kind of data to be expected in the period under review, reference will be made to a wide range of specific payloads. Performance figures quoted have been estimated by the author where not provided by the individual experimenter and and attempt has been made to achieve overall consistency in the criteria for judging experimental performance. The current observational aims of X-ray astronomy may be summarized as follows: (1) The detection of new sources, obtaining approximate positions and intensities. (2) Determination of accurate source positions, to facilitate identification studies. (3) Measurement of the size of a source and, if extended, also its structure. (4) Measurement of the detailed spectrum over a wide energy band for both discrete sources and the diffuse background radiation. (5) Study of source variability. (6) Measurement of polarization of the X-radiation.