The first station on the site was opened in 1863 by the Wycombe Railway, which in 1867 was taken over by the Great Western Railway. In 1868 the Aylesbury and Buckingham Railway (later part of the Metropolitan Railway) reached Aylesbury. It was served by the Metropolitan Line until 1961.
The connecting station with the Metropolitan line is now Amersham Station
The Wikipedia article is at [1] and the Chiltern Railways page is [2]. Some information on the historical services here