A study was conducted to evaluate the effect of gauge length on the short-term performance of visually graded Select Structural and No. 2 kiln-dried nominal 38 × 89 mm spruce-pine-fir lumber in tension parallel-to-grain. The short-term tensile strength properties of three groups of lumber, matched for modulus of elasticity and having gauge lengths of 2642, 3683, 4877 mm, were obtained from test results where the effect of gauge length was isolated from the effect of grade. The performance of the lumber was evaluated by first-order second-moment reliability analyses. In the analyses, the lumber was treated as single tension members under uniform tensile stress along the member length, undergoing snow load conditions at various locations in Canada. The results indicate that the performance factor for Select Structural spruce-pine-fir lumber in tension parallel-to-grain should be multiplied by a factor of 0.92 to adjust for doubling the length from 2500 to 5000 mm to achieve a common reliability index of 3.0. The effect of doubling the length from 2500 to 5000 mm on the performance of No. 2 spruce-pine-fir lumber appears to be negligible.Key words: length effect, tensile strength, lumber, performance factor, reliability index.