Klashorst was born in Santpoort and graduated cum laude from the Gerrit Rietveld Academie in Amsterdam in the early nineteen eighties. During this period a new art movement arose in Europe, “The New Wild Ones”. Klashorst became one of its leading personalities. In 1983 he received a prestigious Dutch Royal award (Koninklijke Subsidie voor de Vrije Schilderkunst) from Queen Beatrix.

Klashorst was one of the initiators of “After Nature”, an international art collective that aimed at reinventing painting and bringing art back to society and taking it out of the official highbrow art world. The collective “After Nature”, including co-founders Klashorst and the artists Roberto Cabot, George Dokoupil, Jurriaan van Hall,  Bart Domburg, Donker brothers and Ernst Voss, opposed the prevailing non-figurative style and was interested in just painting what they saw.

During this period Klashorst could often be found in New York’s East Village art scene where he showed his work in galleries at Manhattan’s Lower East Side, for instance the Daniel Newburg Gallery and the International With Monument Gallery. He hang out with Robert Mapplethorpe, Keith Haring,  and Jeff Koons still at the beginning of their careers.