This paper deals with the accurate measurement of longitudinal off-axi
s bending compliances of composites using four-point bending tests. Th
e effect of supports that induce additional twisting moments is examin
ed analytically, numerically and experimentally. A new testing device
allowing the rotation of the tested sample about its principal axis is
described and used to assess longitudinal bending compliances of seve
ral specimens. It is shown that usual four-point bending devices provi
de apparent compliances that are lower than actual ones.