Steroid hormone receptors are involved in the regulation of tumor growth. Two progesterone receptor (PR) isoforms have been identified in humans: a larger form (PR-B) and the N-terminally truncated one (PR-A). PR isoforms can exert opposite functions and are differentially regulated by estrogens. PR have been detected in several brain tumors including chordomas, however, it is unknown which PR isoform is expressed in brain tumors. The aim of this study was to determine by reverse transcription-polymerase chain reaction (RT-PCR) and by immunohistochemistry the expression pattern of PR isoforms in chordomas as well as its correlation with the expression of estrogen receptor a (ER-alpha). All studied chordomas expressed both PR and ER-alpha. PR-B was the predominant isoform in chordomas both at the mRNA and at the protein level. These data suggest that PR-B should be the predominant PR isoform expressed in human chordomas.