Experimental investigations on soft x-ray lasers based on optical field ionization of gases with an ultrashort-pulse terawatt laser system are presented, The x-ray laser active medium was created using an elongated gas puff target formed by pulsed injection of a small amount of gas from a high-pressure electromagnetic valve through a nozzle in the form of a slit. The target was irradiated with a laser pulses from a 20-fs, 50-mJ Ti: Sapphire (Ti:S) laser system Both recombination and collisional soft x-ray laser scheme have been studied. Soft x-ray spectra from nitrogen. oxygen and xenon targets are presented and discussed.