The Reports on Astronomy 1976 contains the XVIth triennial worldwide review of the progress of astronomy, as written by the Presidents of the forty Commissions of the International Astronomical Union, and refers to the progress in astronomy during the three years 1973, 1974 and 1975, in the fields of each of the Commissions. Strong attempts have been made to ensure that the individual contributions have the character of a critical overall review, where a fairly complete summary is given of the major developments and discoveries of the past three years, and in which the broad developments and new trends are clearly outlined, while at the same time essential problems for future research are identified.

The Commissions of the International Astronomical Union cover the whole field of astronomy, from Ephemerides, Celestial Mechanics, Positional Astronomy, Instruments and Techniques, to topics like High Energy Astrophysics, Astronomical Observations from Outside the Terrestrial Atmosphere, Cosmology Other Commissions deal with the Planetary System like the Commissions for Solar Activity and Solar Radiation, Comets, Planets and Satellites, The Moon, etcetera. Others with Stars and the Galactic System.

For the first time the Reports on Astronomy have been arranged into three volumes of moderate size and as much as possible homogeneous contents. This system will allow a wider circulation of the separate volumes to members of the IAU and other scientists interested in particular topics of astronomical research.