Proton T-2 relaxation and n.m.r. imaging experiments were utilized to study the molecular mobility and heterogeneity of cis-1,4-poly isoprene crosslinked with dicumyl peroxide in the presence of triallyl cyanurate (TAC) and zinc diacrylate (ZDA) as coagents. It was observed that the long T-2 relaxation times of the rubber protons in peroxide/TAC or peroxide/ZDA crosslinked elastomers decrease with the increase in the crosslink density resulting from the addition of peroxide or coagent. The T-2 relaxation times of protic solvent in swollen rubber are also affected by the physical property changes of the networks induced by peroxide and coagent addition. It was concluded that the solvent T-2 relaxation times depend on solvent-polymer interactions as well as the crosslink density of the networks.