The binding of ligand by cytoplasmic Androgen Receptor (AR) is a critical step in androgen signalling. In the cytoplasm, unliganded AR requires the recruitment and activity of several factors and chaperones that stabilise the receptor preventing its degradation and maintaining it in a ligand-binding competent state. Heat shock protein 90 (HSP90) and p23 are essential components of this apo-receptor complex for the AR as well as several other steriod receptors. p23 is a highly conserved ubiquitously expressed protein that is best characterised as a co-chaperone of HSP90 but appears to have some independent chaperoning activity also. Recently, p23 has been shown to inhibit the activity of glucocorticoid receptor but enhance activity of the oestrogen receptor by increasing its ligand binding activity.