Mass at ten u a tion co ef fi cient of lead-based ce ram ics have been mea sured by ex per i men tal meth ods and com pared with the o ret i cal and Monte Carlo sim u la tion re sults. Lead-based ceram ics were pre pared us ing mixed ox ide method and the X-ray dif frac tion anal y sis was done to eval u ate the crys tal struc ture of the pro duced hand made ce ram ics.The ex per i men tal re sults show good agree ment with the o ret i cal and sim u la tion re sults. How ever at two gamma ray ener gies, small dif fer ences be tween ex per i men tal and the o ret i cal re sults have been ob served. By add ing other ad di tives to ce ram ics and ob serv ing the changes in the shield ing prop er ties such as flex i bil ity, one can syn the size and op ti mize ce ram ics as a neu tron shield. Key words: at ten u a tion co ef fi cient, CsI(Tl) de tec tor, lead-based ce ramic, MCNP-4CA. Vejdani-Noghreiyan, et al.: The o ret i cal and Ex per i men tal De ter mi na tion of .