The period covered by this report, July 1987 to June 1990, witnessed a similar activity as the previous triennial interval. While the latter saw the successful encounters of several space probes with comets P/Giacobini-Zinner and P/Halley as well as the unprecedented worldwide campaigns of ground-based measurements organized by the International Halley Watch, emphasis during the 1987–1990 time period focussed mostly to the analysis of existing data, while the study of new comets continued at a slightly increased level.