Fire protection of structural steel is achieved largely through the use of coatings or encasement of steel members. Coatings are effective, but their replacement with fire-resistant steels possessing enhanced high-temperature strength could improve aesthetics, reduce construction costs, and increase the competitiveness of steel. The elevated temperature properties of four microalloyed steels (C-Mn, 0.02Nb, 0.5Mo-0.02Nb, and 0.05V-0.02Nb) and one copper containing steel (1.0Cu) were examined at temperatures up to 700°C. The addition of molybdenum (0.5wt%) and niobium (0.02wt%) to C-Mn steel resulted in preservation of room temperature yield strength levels at 350°C, and two-thirds of room temperature yield strength up to 600°C. A V+Nb steel exhibited similar high temperature strength. The copper containing alloy was heat treated prior to testing to evaluate three alloy conditions: copper in solution (available for precipitation), “ideally aged” (maximum copper precipitation strengthening), and over-aged. Copper in solution (versus aged) prior to mechanical testing was shown to have the highest elevated temperature yield/tensile strengths relative to room temperature strength. This mechanism is likely to be applicable to other precipitating species as well. A new test method capable of simulating material behavior during a fire was also developed and used to evaluate the five chosen steels. During the test a constant load is applied to the test sample at room temperature while temperature is increased at a predetermined rate. Temperatures associated with the onset of plastic deformation and failure are monitored. Consistent with tensile testing, the Mo+Nb steel resisted yielding and failure to higher temperatures than the other microalloyed steels tested. However, the V+Nb alloy exhibited lower yielding and failure temperatures versus the other microalloyed steels in the constant load test. Copper in solution (versus aged) prior to mechanical testing led to higher yielding and failure temperatures in constant load tests, just as with elevated temperature tensile tests.