This paper examines how bank relationships affect firm performance. An empirical implication of recent theoretical models is that firms maintaining multiple bank relationships are less profitable than their single-bank peers. We investigate this empirical implication using a data set containing virtually all Norwegian publicly listed firms for the period 1979-1995. We find a robust and economically relevant negative two-way correspondence between the number of relationships and sales profitability. We also find that firms replacing a single relationship are on average smaller and younger than those firms choosing not to replace a single relationship.