The transient elongation behavior of semi-dilute and concentrated polyethyleneoxide and polystyrene solutions has been investigated using CaBER in vertical and horizontal position. PEO was dissolved in different polyethyleneglycol (PEG) / water mixtures in order to study the effect of solvent viscosity. The horizontal stretching (tilted CaBER method) allows for the determination of the axial force F during the capillary thinning. The transient force ratio X(t) (ratio of F and the force caused by surface tension) decreases exponentially with time and levels off to X ≈ 1 for the PEO solutions with concentrations lower than the entanglement concentration. For PS solutions X(t) shows a more complex behavior including a Newtonian controlled thinning regime. The characteristic time constant of the exponential decaying X(t) is equal to the elongational relaxation time λe obtained from filament diameter thinning for both polymers. For the PEO solutions the relaxation time ratio λe / λs, where λs is the longest shear relaxation time, is independent of solvent viscosity. The true transient elongational viscosity ηe(t) has been compared to apparent values ηe,app(t) obtained under the assumption of a vanishing axial normal stress. In the initial period of thinning ηe(t) is much larger than ηe,app(t) but decreases whereas ηe,app(t) monotonically increases. Then ηe(t) goes through a minimum and beyond that both values are roughly the same and increase exponentially. The Trouton ratio calculated from the minimum elongational viscosity and the zero shear viscosity, decreases with increasing polymer concentration and approaches a constant value when the entanglement concentration is reached.