Reduced speech fluency is frequent in clinical paediatric populations, an unexplained finding. To investigate age related effects on speech fluency variables, we analysed samples of narrative speech (picture description) of 308 healthy children, aged 5 to 17 years, and studied its relation with verbal fluency tasks. All studied measures showed significant developmental effects. Speech rate and verbal fluency scores increased, while pauses, repetitions and locution time declined with age. Speech rate correlated with semantic fluency tasks suggesting that it also depends upon the efficacy of lexical retrieval. These results indicate that the interpretation of disorders of speech fluency in childhood must incorporate age appropriate norms.