Smooth tensile. specimens were machined from a round Ti6Al4V bar, the crystallographic orientation of which was determined by X-ray diffraction analysis. The preferred orientation was mainly [<10(1)over bar 0>] texture. When the specimens of various hydrogen contents were slowly strained, those having more than 2000 p.p.m. hydrogen exhibited slow-strain embrittlement in both rolling and transverse directions, whereas below 2000 p.p.m. hydrogen, the effect of hydrogen on the tensile properties was different in the two directions. Hydrogen decreased both the proportional limit, sigma(0) and the 0.2% flow stress, sigma(0.2), in specimens parallel to the rolling direction but there was no change in either sigma(0) or sigma(0.2) with increasing hydrogen content in the transverse specimens. The strain hardening behaviour of all specimens could be divided into two stages, whatever the orientation of specimen or hydrogen content. The first-stage strain-hardening exponent, n(1), increased with increasing hydrogen content, but n(1) for the transverse specimens was smaller than for specimens parallel to the rolling direction, and the variation of n(1) with hydrogen content was also lower in the transverse specimens. These differences were attributed to the differing deformation modes for specimens of different orientation. There was, however, no effect of orientation on the micro-fractography.