Following a discussion of flashtube impedance and its dependence upon discharge current, the relation between current magnitude, initial charge voltage, circuit constants, and lamp dimensions is derived for lamps operating in pulse forming networks of cascadedLCpisections. The resulting equation,I=0.27(d/l)23(C/L)13V43, has been experimentally verified by data from flashtubes having arc lengths ranging between 7.6 and 91.5 cm. When, as is often the case, a flashtube is operated in series with a single inductor, the current pulse is not rectangular and the assumption of constant discharge resistance used in the multisection line study is invalid. A more precise analysis has been carried out with the aid of a digital computer in which the differential equation for a series RLC circuit is solved with the nonlinear conditionR=Rw+R(i). Inclusion of wiring resistanceRwpermits further extension of the solution's applicability and the results are found to agree well with experiment.