For the first time, the successful Gilch synthesis of poly(ortho phenylene vinylenes) (ortho-PPVs) is reported. The molar mass of the constitutionally homogeneous ortho-PPVs reaches values as high as M-w approximate to 300 000 Da. The ortho-connectivity of the repeating units forces the chains to assume closely packed conformations even in good solvents. Significant perturbation of the pi-electron systems and considerable shortening of the conjugation lengths are the consequences. UV-vis absorption and photoluminescence maxima consequently are shifted clearly toward shorter wavelengths compared to, e.g., classic para-PPVs.