We present an investigation to study the degradation of poly(methylmethacrylate) (PMMA) based resists during electron beam exposure and their development characteristics. After exposure to the electron beam we detect for ARP 610 resist (PMMA 74%, PMAA 26%) and for a homopolymeric PMMA resist, a similar bimodal respectively multimodal molecular weight distribution curve characterized by a shift of the maximum from105to103g/mol and an increase of low molecular weight fractions(≈103g/mol) with increasing exposure dose. The model of Greeneich can only be applied to lower deposited energy densities (ARP610<4eV/nm3,homopolymeric PMMA<8eV/nm3).The difference found between experimental data and modeling values at higher deposited energy densities for both resists, results from a formation of stable low molecular weight fractions. Comparing the measured dissolution rate with the calculated one, the determined difference proves the nonapplicability of the empirical formula for the dissolution rate given by Greeneich. The low molecular weight fractions influence the dissolution rate significantly more than given by their portion in the molecular weight distribution.