This paper reports the experimental left-handed behavior of two transmission lines in waveguide technology based on split ring resonators. Two miniaturized waveguide-encapsulated structures have been analyzed in terms of their left-handed behavior and especially in terms of losses. They are respectively implemented in a !Inline technology combining single split ring resonators (S-SRRs) and short-circuiting wires for the first and in waveguide technology using double-SRRs combined with inductive windows for the second. Experimental evidence of the left handed behavior of both guiding systems is achieved via the analysis of the frequency dependence of phase offset between two different length lines. A careful analysis of the EM behavior of these structures reveals differences in terms of their EM operation as well as similarities in terms of loss considerations. Making use of these novel frequency selective lines, very compact devices in terms of the longitudinal dimensions can be synthesized in order to take advantage of their negative refractive index