The uniaxial extensional rheology behaviour of tailor-made long-chain branched TFE(39)/HFP(11)/VDF(50) terpolymers, LCB-THVs, is investigated at 265 degrees C using the extensional viscosity fixture ( TA Instruments). Within the window of applied extension rates (0.03 s(-1) <= epsilon* <= 30 s(-1)) the model polymer fluids show weak to marked strain-hardening behaviour depending on their level of branching. A straightforward data filtering and evaluation procedure capable to extrapolate for quasi steady-state conditions from the similarity of the data sets is presented. Flexible approximation functions for the nominal transient elongational viscosity curves eta(+)(E)(t, epsilon(center dot)) and for quasi steady-state elongational viscosity curves. eta(double dagger)(E)(t, epsilon(center dot)) are proposed. In the latter case, there are three adjustable parameters employed which have the physical meaning of: the elongational stress response time t controlling the location of the maximum in the. eta(double dagger)(E)(t, epsilon(center dot)) function, the polydispersity. of a unimodal LCB population, and its effective amount. An approximation function is also proposed for bimodal LCB distributions, which applies very well for the LDPE IUPAC A standard resin. Empirically, tau is found to depend on the size dimension of branching lambda, derived from molecular characterization, by the relationship tau similar to lambda(3.3).