We examined whether infants could visually discriminate the orientation of a grating surrounded by an oblique square (experiment 1) and a vertical square (experiment 2). A familiarisation-novelty preference procedure was used. In experiment 1, infants aged 4 to 6 months did not visually distinguish the orientation of a grating surrounded by an oblique square. However, in experiment 2, in which a vertical surrounding square was used, such infants visually distinguished the orientation of a grating. Our results suggest that the external visual frame can affect infants' perception of the orientation of a grating, as it does in adults. In experiment 1, a grating was within an oblique square. Here, the relative orientation with respect to the external visual frame differs from the orientation relative to the retinal/gravitational axes. Such discrepancy appears to cause confusion in infants' perception of orientation.