A strap adjustable brassiere has straps that are slidably engaged with a band rail extending along the wing band and/or a cup rail extending along the cup. The wing band rail extends in an incline from a side position toward the center back position and this enables the straps to be slid from one position to another along the band rail without changing the length of the straps. Likewise, the cup rail extends at an incline from a side location toward the center front location to allow the strap to slide along the cup rail without changing the length of the strap. The rail may be a bulbous extension from the wing band and the strap slider, cup or band, may have a cavity that extends around the rail to provide a slidable engagement.