The Telephone Operating Group of GTE Corporation embraces about 11. 5 million telephone lines within the continental USA. This customer base is served by 2,250 central offices (COs) or telephone exchanges. Long range service planning efforts indicated a need for an analysis of the two-wire local loop including physical attributes such as construction, gauge distribution, length, the transmission performance and an assessment of its digital signal carrying capability. During 1982 a survey of GTE customer loops was completed and a database was created. The physical loop data, along with other loop measurements including crosstalk attenuation, impulse noise and insertion loss contributed to the modeling of GTE's local loop. An analytical model has been developed for predicting the error probability performance (as a function of signal-to-noise ratio) of the loop plant for digital communications use. The model permits evaluation of loop grooming activities, different service speeds and various noise environments and their impact on the penetration of digital services into the existing loop plant. The authors report on the plant survey and analysis as well as the analytical model and its application.