This paper describes Bantu imperatival and prohibitival speech acts. The study is set against the background of the formal instability of directives and grammaticalization theory. On the basis of a sample of 100 languages, we conclude that imperatival strategies are limited to imperatives, subjunctives, and indicatives while prohibitival strategies range from negative subjunctives and negative auxiliary constructions through constructions with prohibitive markers and negative infinitives to negative indicatives and negative imperatives. Politeness is shown to play an important role in the development of new strategies, which often have a more polite character and which become neutral themselves over time. We argue that it may even partly explain why prohibitival strategies exhibit more variation than imperatival ones. However, it is also clear that new directive strategies need not be more polite and that politeness is just one of the possible factors contributing to the difference between imperatival and prohibitival strategies.