Speech input has proven to be useful for entering text in electronic documents, and seems to be a promising technique also for writing mathematical expressions. Up to now, there is no evidence about the potential advantages of speech input on blind persons who need to edit scientific documents. This paper introduces a technique to enable blind persons to input mathematics by speech. A system prototype has been developed, based on the LAMBDA mathematical editor and the Dragon NaturallySpeaking^TM software. An early assessment has been undertaken with a group of blind users. The results of this evaluation will be discussed in this paper and will be exploited to enhance the system prototype.