This bachelor essay aims to explore how composition with pentatonic scales can help to expand the vocabulary of a jazz improviser. It also has the purpose of expanding the knowledge of the relationship between harmony and pentatonic scales. I have written five melodies with five different pentatonic scales to see how composing can affect my improvisational skills on the tenor saxophone. The method is to get familiar with the scales, write a melody and then harmonize it.  Composition utilizing pentatonic scales can affect how you improvise. The pentatonic scales provide sounds that can be very useful. I play larger intervals when improvising. It was also beneficial to dig deep into the pentatonic landscape and to find the spiciest notes of each scale. After this study, I have a better knowledge of harmony and the pentatonic scales that can go with it. During this investigation, I have considered doing this again, choosing scales whose span is larger than one octave.