The formative time dependence on working voltages tf(U) in nitrogen is determined: (1) from the Laue diagrams, by taking the values where the linear approximation of the electrical breakdown time delay (td) intersects the time axis, (2) from histograms, by taking the minimum values of the delay times for the formative time, and (3) from a difference tf = [Formula: see text] – [Formula: see text] ≈ [Formula: see text] – σ (td), where standard deviation σ,(td) is approximately equal to the mean of the statistical time delay [Formula: see text]. The breakdown time delay measurements are supported by oscilloscopic measurements of the voltage drop and the current rise time during inception of the discharge. Several simple models were applied to describe the experimental formative time dependence on working voltages tf,(U) and a good agreement with experimental data was found.PACS Nos.: 51.50.+v, 52.80.–s