This work comprises methyl-tert-butyl ether's (MTEE) toxicological data. It has been completed in 1972 under ANIC S.p.A.'s, sponsorization. ANIC S.p.A. (a company of the ENI group) is an operating company which produces fertilizers, fibers, elastomers, chemical products a.s.o. and has put in operation in 1973 the first plant in the world for manufacturing MTBE to be used as gasoline coaster. The plant has the capacity of 100.000 MT/y. In-1972 for performing the present work,--the MTBE was identified-as Cl and C15B and therefore it is so identified also now in the work. The above mentioned ANIC plant is located in Ravenna (Italy) and was designed by SNAMPROGETTI S.p.A. that has also provided all the relevant engineering services. Snamprogetti is the engineering company inside the ENI group and is encharged for the design, construction and supply of any kind of engineering services connected with the construction of chemical plants. This work is divided in book I, book II and book III. The book I - sub-divided in two parts and namely book I/1 and book I/2 - contains the majority of the toxicological data and has been completed on July 31st, 1972. The book II is an abstracts of the works subject matter of the book III. This latter is an integration of the data shown in book I since medium - and long - term tolerance data for different types of mixtures are referred to.