AbstractA series of 1‐(3‐pyridyl)‐1‐substituted‐but‐3‐yn‐1‐ols and some related compounds were synthesised and tested for antifungal activity against eight phytopathogenic fungi of different taxonomic classes. High activity was shown in particular againstSphaerotheca fuligineaonCucumis sativus.The compounds containing aromatic substituents gave the best results, not only in protectant but also in systemic and eradicant tests. The quantitative structure‐activity relationship suggests that steric effects play an important role in determining