Drug release of watersoluble active agent (ephedrine hydrochloride) and water-insoluble ones (griseofulvine, salicylic acid, sulfadimidine) from hydrogels containing different polymers was investigated. The rheological behaviour of polymer matrices was characterized by flow curves and viscosity curves. These hydrogels were not thixotropic systems, unlike more authors' statement. The values of rheological constants increase exponentially with concentration of polymers. The liberation of active agents can be characterized by a multiplicative function. The constant of viscosity vs. concentration function was determined and it was called as characteristic of structure formation. A linear relationship between constant of structure formation and drug liberation was demonstrated.