Two SiO2-filled di-Me siloxane networks with different molar masses, Mc (22000 g/mol and 33000 g/mol), between the junctions have been investigated by simultaneous mech. and FTIR spectroscopic (rheooptical) measurements to monitor the structural changes in cyclic elongation-recovery procedures. Higher polymer chain orientation was obsd. at corresponding elongations for the low-Mc network, but due to the higher extensibility appreciable strain-induced conformational regularity occurred only in the high-Mc material. Differences with ref. to unfilled model networks are pointed out.