We propose a detailed investigation of the properties of the dust emission features associated with Polycyclic Aromatic Hydrocarbons as seen towards many galactic and extragalactic sources. This study will concentrate on the PAH features in the 5 to 12 micron range as observed towards galactic HII regions. Earlier low resloution (R 250) SWS AOT1 observations show very clear variations in the PAH spectrum in this wavelength range. Theoretical calulations indicate strong dependence of the details in the PAH spectrum depending on composition of the emitting material. Comparing the proposed high resolution observations to these models will allow us a a detailed investigation into the composition of the PAHs and their ionisation state.