Dichloropyrazino-oxazines of the formula ##STR1## wherein R is H or a C.sub.1 to C.sub.8 alkyl, alkenyl, cycloalkyl or cycloalkenyl radical, are disclosed. The compound in which R is H has utility as an intermediate for the compounds in which R is other than H. The latter compounds exhibit microbicidal, herbicidal or insecticidal activity. The compounds of the invention are readily prepared from tetrachloropyrazine and 2-aminoethanols of the formula R--NH--CH.sub.2 CH.sub.2 --OH.