Dataset on preference votes received by Christian Democratic (DC) and Socialist Party (PSI) candidates in the elections for Legislatures I-XI to the Chamber of Deputies (1948 to 1992). During this period, Italy used a relatively pure version of open-list proportional representation. Until the 1992 parliamentary elections, voters could optionally indicate their preference for as many as three (or in districts with 16 or more representatives, four) candidates from the party list they selected. As of 1992, voters could use only a single preference vote. Typically, only about 30 percent of Italian voters used any of their available preference votes. Individual candidates were seated according to the number of preference votes received, while the number of seats won by each party was determined by the number of list votes received by the party. The number of seats (district magnitude) in Italy's 31 electoral districts using proportional representation (a 32nd electoral district, the Valle d'Aosta, was a majoritarian single member district) ranged from 4 to 53, with the average around 20. Parties listed as many candidates as there were seats, and individuals could stand in as many as three districts simultaneously, as well as simultaneously for the Chamber of Deputies and the Senate. Starting with the elections held in 1994, the electoral system was substantially altered, and a mixed PR/majoritarian system used. It is not possible to match electoral districts before and after 1994. (This description of Italy's electoral system is taken from Douglas Wertman, "The Italian Electoral Process: The Elections of June 1976," in Italy at the Polls: The Parliamentary Elections of 1976, ed. Howard R. Penniman (Washington, D.C.: American Enterprise Institute, 1977).) The dataset includes the number of individual-level preference votes received by each Chamber candidate for the DC and PSI, the candidate's party affiliation, the candidate's district number, the candidate's legislature number, whether the candidate was elected or not, and whether, having won, s/he choose to be seated in another district or for the upper house instead.