This paper presents research on integrating context-dependent durational knowledge into HMM-based speech recognition. The first part of the paper presents work on obtaining relations between the parameters of the context-free HMMs and their durational behaviour, in preparation for the context-dependent durational modelling presented in the second part. Duration integration is realised via rescoring in the post-processing step of our N-best monophone recogniser. We use the multi-speaker TIMIT database for our analyses.