Research has been undertaken to demonstrate the effect on z-strength of headbox consistency in one-sided versus two-sided roll forming of unbleached softwood kraft pulp over a wide range of jet to wire speed differences. In addition, formation and tensile strength were evaluated. Using a pilot machine, each forming method was examined at two headbox consistency levels (0.4 and 0.6%). The wire speed was varied from 550 to 660m/min while maintaining the headbox conditions, resulting in a change in grammage from approximately 71gsm to 61gsm. A significantly higher Z-strength was noted for one-sided roll forming at a headbox consistency of 0.4% compared with two-sided roll forming. However, an increase in consistency resulted in a ore similar Z-strength through a larger reduction in Z-strength efficiency for one-sided than two-sided roll forming. In addition, Z-strength was promoted by formation improvement through the jet to wire speed difference in both one-sided and two-sided roll forming of the furnish. The effects of the jet to wire speed difference on formation and tensile strength efficiency in one-sided roll forming of the present furnish were relatively more favourable and more similar to the effects in two-sided roll forming.