The internal dynamics of actin filaments and the rheological properties of transiently and chemically cross‐linked actin networks were studied by quasielastic light scattering and a new type of rheometer. Evidence is provided that the actin solutions exhibit typical universal properties as solutions of high molecular weight polymers exhibiting Rouse‐Zimm behavior. A number of power laws is established and the persistence length of actin filaments is determined as &lgr;≊0.3 &mgr;m.