Flake alignment level (FAL) is a primary variable in oriented strandboard (OSB) manufacture that significantly affects the properties of OSB panels such as linear expansion (LE). Realizing the differences of FAL and LE among various OSB manufacturers will help the users have a better understanding of OSB performances in utilization. FAL and LE of various commercial OSB were investigated in this study. FAL was analyzed through percent alignment (PA) proposed by R. L. Geimer. This measures the average angle deviation from a reference angle of 45 degrees to the principal alignment direction of the board. It was found that different OSB manufacturers and even the same company showed significant variations in PA. In general, the front sides of panels had superior PA compared to the back sides. LE of commercial OSB had no clear relationships with PA. So it is hard to predict LE from flake alignment for commercial OSB.