AbstvaetTho batsic nature of feasible scheduLes and their Iot sizes arc investigated for a single-machine multi-product problem, u"der the assumpt,ions of det,ermmistic demand on infinite tirne horizon and,cyc}ic productiori sequence. Feaslble schedule is obLained under t,he balaiiced lot size which is in proportion to the dernand rate of each product, atid independent of production sequence.It is determined uniquely if the product,ion rate is higher than the sum of deinand rate, while there are infinit,ely many feasibEe schedules if the production rate is just balanced to the surn of dema"d rate. 'I"he quantitative re]ation between such related factoTs as demand rate, production rate, machine idle Lime, production Iot size, can be a practical guide for designing a small lot, sizc production systein, as well as clctermining a fea$ible schedule on Iong-term finite plui'ming period, The OpeiationsReseaich Society of Japan 12O ff, Kono di Z, ,'Vinkamttra determining a pruduction schedule. [I]he whole discussion will be done on a inodel ef a stationary case with deterministi(; deinand on infiniLc time horizon and cyclic repetit;ion of a production sequence, 2. Model Formulation 2.1 Basic assumptions and notations (1) On infinite time horizon [0, Do), product deniand rates a,re deterministically given by coiistant Di > O for product i,i:[ 1,2,・・・,r.(2) Only one product can be produced at a time, Production ratc of produ(;t i is given by constant Ki > O,i = 1,2,・・・,r. Fer the sake of simplification, each Di a,nd Ki shall be counted by its own produci,ion rate as one unit,, so that Ki --1,i = ],2,・・・,r,