Combined generation o f p o w e r and heat o f f e r s g r e a t economic advantage and s e r v e s t h e r e q u i r e m e n t s o f environmental conservation. However the operation o f such i n t e g r a t e d "cogeneration s y s t e m s " is a complex problem. because the demand o f e i t h e r p o w e r and heat m u s t be provided simultaneously w i t h r e g a r d t o many d i f f e r e n t c o n s t r a i n t s . This paper r e p o r t s on the development o f an advanced procedure f o r s h o r t t e r m operational planning in cogeneration s y s t e m s based on t h e method o f Mixed Integer Linear P r o g r a m m i n g completed by some supporting measures f o r p r o b l e m reduction. T e s t r e s u l t s f o r sample s y s t e m s derived f r o m actual cogeneration s y s t e m s indicate the p r o c e d u r e ' s capability of calculating optimal economic schedules under r e a l i s t i c conditions. KEYWORDS operational planning, cogeneration o f power and heat, M i x e d Integer Linear P r o g r a m m i n g 1.