Photodefineable cyclobutarene compositions are disclosed. These polymer compositions are useful in composites, laminates, membranes, films, adhesives, coatings, and electronic applications such as multichip modules and printed circuit boards. An example of such photodefineable cyclobutarene compositions is a mixture of a photosensitive agent such as 2,6-bis(4-azidobenzylidene)-4-methylcyclohexanone and a cyclobutarene such as oligomeric divinyltetramethyldisiloxane bisbenzocyclobutane.