Abstract A brief summary of the work from 1972 to 1981 of the International Geological Correlation Programme's Project No. 29, Working Group on the Precambrian-Cambrian boundary, is given and the position reached in the opinion of the author in the first quarter of 1981 is outlined. Two figures give both the coverage of the Project's research in global terms and tentative conclusions regarding the position of the Precambrian-Cambrian boundary in selected critical sections. Plenary decisions of the Working Group at conferences in Paris (1974) and Cambridge (1978) are outlined. In conclusion, the stratigraphic value of archaeocyathid zonation, small Tommotian shelly fossils, trace fossils and trilobites are discussed and the main problems thought to remain in the next few years are noted: 1. (1) location and accessibility of the global boundary section and point, possibly in Asia; 2. (2) intercontinental correlation; 3. (3) palaeobiological research.