AbstractData on tensile strength and elongation at break for a series of Viton A‐HV vulcanizates are discussed. The data were obtained at various extension rates at temperatures from −5 to 230°C (25 ≲T—Tg≲ 260°C) on seven vulcanizates having crosslink densitiesve(estimated from C1in the Mooney‐Rivlin equation) from 0.46 × 10−5to 24.4 × 10−5mole/cm3. At an extension rate of 1 min−1, an increase inveaffects the tensile strength σb(based on the undeformed cross‐sectional area) and the true tensile strength σbσb(based on the cross‐sectional area of a deformed specimen) as follows: σbis essentially constant at a low temperature; it passes through a decided maximum at intermediate temperatures; and it increases to a plateau at elevated temperatures. In contrast, λbσbdecreases markedly at all temperatures, an exception being the most lightly crosslinked vulcanizate(s). Application of time—temperature superposition to the ultimate‐property data gave logaT; its temperature dependence is that typical of nonpolar rubbery polymers. Data on the vulcanizates were compared in corresponding temperature states by plotting log 273σb/T, log 273λbσb/T, and (λb— 1)/(λb— 1)maxagainst logtb/(tb)max, wheretbis the temperature‐reduced time to break and (tb)maxis the value at which the ultimate extension ratio λbattains its maximum, (λb)max. Except for the most lightly crosslink vulcanizate, the comparison shows that 273λbσb/Tand (λb— 1)/(λb— 1)maxare substantially independent of (or only weakly dependent on) crosslink density, that 273λb/Tincreases withve, and that