In this paper, I will describe and discuss the extinct Uru variety of Ch'imu/Lake Titicaca (Peru), as documented by the German researcher Walter Lehmann (1878–1939). To this purpose, I will compare the Ch'imu Uru to the closely related varieties of Irohito Uru and Chipaya (both Bolivia), relying on archival material and previous studies. The topics I will take into consideration include phonological and etymological features as well as grammatical markers and constructions, such as e.g. personal and possessive pronouns and negation. Based on the findings of my investigation, I will critically discuss the utility of Lehmann's Ch'imu data for further research.