Tontemboan is bordered on its north by the Tondano and Tombulu languages (which are also Minahasan languages), and on its south by Bolaang-Mongondow. The Tontemboan language area stretches like a belt across the northern peninsula of Sulawesi, from Langowan in the east through Sonder to Amurang on the west coast, then southward, practically encircling the smaller Tonsawang language.
Tontemboan comprises two dialects: the Makelai dialect in the east (centered around Langowan, but also spoken in Tompaso in the southwest), and the Matenai dialect in the west (centered around Sonder and Kawangkoan, also spoken along the west coast) (Sneddon 1978:5; Merrifield 1991:79; Merrifield and Salea 1996:27).
In 1970, Sneddon estimated there were around 140,000 Tontemboan speakers, making Tontemboan the most populous of the Minahasan languages (Sneddon 1970:17). Owing to language decline, the number of speakers in the present day is undoubtedly less, but no recent estimates are available.
Merrifield, Judi. [1991.] Life in North Sulawesi. Unpublished typescript, vii, 107 pp.
Merrifield, Scott; and Martinus Salea. 1996. North Sulawesi language survey. (Summer Institute of Linguistics Publications in Sociolinguistics, 1.) Dallas: SIL.
Sneddon, J. N. 1970. The languages of Minahasa, North Celebes. Oceanic Linguistics 9:11–36.
Sneddon, J. N. 1978. Proto-Minahasan: Phonology, morphology and wordlist. (Pacific Linguistics, B‑54.) Canberra: Australian National University.