Thi s pa pe r fir st di sc usses th e tec hniqu e of mak ing S ta rk meas u re me nt s a t millim ete r wave' le ng th s. Th e de tail s of correcting for res idu a l ove rl a p betwee n th e lin es, th e effec ts of modu la ti on , a nd of th e fi e ld inh o moge ne it y a re di sc usse d. Finall y th e meas ure d fre qu e nc ies a nd th e e mpiri ca l S ta rk coe ffi cie nt s for one H,O, a nd one D,O, an d fiv e HDO lin es be tw ee n 85 and 250 GHz a re give n .Th e fi na l a nalys is of the data to giv e values of th e dipole mome nt wi ll be give n in a noth e r pap er.Key word s: Millimeter wav es; S ta rk e ffec t; wat e r.