Ireland is often described as the odd country out in studies of west European politics. Its parties do not readily fit into the classical European definitions of party families. This paper estimates the positions of the parliamentary parties since 1937, based on a dataset consisting of all parliamentary votes from 1937 to 2006 using a Bayesian ideal point estimation framework. It is shown that party competition in the Irish parliament adheres to a government-opposition dimension, and that it is possible to distinguish only two blocs of parties in each period, one consisting of the parties supporting the government and one comprising the remaining parties as the opposition. It is argued that the estimated positions do not reflect party policy positions but are instead voting cohesion of two distinct blocs of the parliamentary parties. The findings are validated by a comparison with various expert surveys of Irish party positions.