Long- or continuous-fibre-reinforced polymers often show a significant difference between the tensile and flexural strength. Both higher and lower values of the flexural strength, relative to the tensile strength, are observed. Lower values are often caused by the occurrence of fibre microbuckling at the compression side of the specimen. This paper presents a relationship between the average microbuckling stress in the microbuckled cross-sectional area, the tensile strength and the flexural strength. It is found that the flexural strength may be significantly higher than the fibre microbuckling stress. (C) 1999 Elsevier Science Ltd. All rights reserved.