Signs with handshape variants were analyzed for patterns of handshape relationships in American Sign Language. On the basis of this analysis, a set of 57 handshapes are proposed which are distinct at the morpho-phonemic level of the language. A new set of 26 morpho-phonemic handshape features are proposed to describe these handshapes. These features are tested on all the signs listed in the DICTIONARY OF AMERICAN SIGN LANGUAGE, in an attempt to work out more general handshape relationships within the total lexicon. In order to do this, a new theory about the structure of the sign language lexicon is proposed, which utilizes two types of features: Primary morpho-phonemic type features and Secondary, more purely perceptual type features. Both historical and synchronic patterns of the handshape in American Sign Language seem to be better explained by this new set of handshapes and this combination of morpho-phonemic and phonological level features within the total framework of the proposed lexical structure.