Although Proto-Bantu had a vowel length contrast on roots which survives in many daughter languages today, many other Bantu languages have modified the inherited system. In this talk I distinguish between four types of Bantu languages : (1) Those which maintain the free occurrence of the vowel length contrast inherited from the proto language ; (2) Those which maintain the contrast, but have added restrictions which shorten long vowels in pre-(ante-)penultimate word position and/or on head nouns and verbs that are not final in their XP ; (3) Those which have lost the contrast with or without creating new long vowels (e.g. from the loss of an intervocalic consonant flanked by identical vowels) ; (4) Those which have lost the contrast but have added phrase-level penultimate lengthening. I will propose that the positional restrictions fed into the ultimate loss of the contrast in types (3) and (4), with a concomitant shift from root prominence (at the word level) to penultimate prominence (at the intonational and phrase level). In the course of covering the above typology and historical developments in Bantu, I will show that there are some rather interesting Bantu vowel length systems that may or may not be duplicated elsewhere in the world.