Sign language in I anzania is a relatively new field of linguistics that is yet to atttact many researchers and linguists in particulru I anzanian Sign Language (TSL) functions as a unifYing tool for the deaf in the countiy and, probably, beyond. This language, which is still at its early stage of development, is used in the same linguistic environment with Kiswahili, the national language, which is more established The situation leaves TSL disadvantaged and is thus likely to cause a one-way linguistic influence, from Kiswahili to TSL This paper, therefore, examines the nature and impact of the situation Firstly, it focuses on the question ofwhether or not TSL is an independent language that has developed as a sepruate language, quite distinct fiom the spoken languages of the communities that swround it, especially Kiswahili. Secondly, it examines the extent to which Kiswahili has influenced TSl and thus the role that the former plays in leruning and developing the latter The results of the study show that Kiswahili has had some influence on TSL but the influence is mruginal at lexical level Of all the signs studied, only 13% were directly related to Kiswahili The majmity of the signs studied were found to be iconic in nature, but only 12% of all signs were semantically tianspru·ent Even in these cases where the signs rue tiansparent, the tiansparency of the signs is not based on one's knowledge of Kiswahili Most of the tianspru·ent signs are common gestures that any person of any ethnic migin can interpret The study has thus established that TSl is more of a sign language than signed language It is an indigenous African sign language, uruelated to the Western Sign Languages, except for the IIWflUal alphabet. Finally, the study predicts that much of the tianspru·ency and iconicity in TSL will gradually fade away as the language develops across time, space, and generations