Optical and magnetic resonance properties of several [pi]-conjugated polymers were studied and the results consolidated in this thesis. Photoluminescence (PL), electron spin resonance (ESR), and the novel Ultraviolet Optically Detected Magnetic Resonance (UV-ODMR) results on poly(p-phenyleneethynyleneaniline) (PPEA) derivatives are shown. The source wavelength, [lambda][subscript]ex, dependence of the ODMR is investigated on several [pi]-conjugated polymers including poly(p-phenylenevinylene) (PPV), poly(p-phenyleneacetylene) (PPA), and poly(3-alkylthiophene) (P3AT) derivative films. The effects of photo-oxidation on the UV- and laser-excited ODMR of dioctoxy substituted PPV (DOOPPV) films is shown. The ODMR results on unsubstituted PPV and CN-PPV films are described here. ODMR results on poly(p-di(phenyleneethynylene)phenylenevinylene) (PDPEPV) and cyano-PDPEPV are described. Lastly, PL, ESR and light-induced ESR (LESR) results of poly(p-phenylenecumulenes) (PPC) are reported.