The soft X-ray properties of two samples of Active Galactic Nuclei (AGN) are investigated using ROSAT PSPC and ASCA observations. A large sample of optically selected narrow-line type 1 Seyfert galaxies (NLS1) have been studied and the results compared to their optical, infrared and radio properties. The soft X-ray spectra of the majority of the objects in this sample are well characterized by a power law with a mean photon index of <G> = 3.03 ( sG = 0.43), which is significantly steeper than seen in other samples of type 1 Seyfert galaxies and quasars. Rapid and large amplitude variability is observed in many observations and nine objects exhibit super-Eddington behavior where the efficiency exceeds the theoretical maximum for an accretion disk around a non-rotating black hole. The behavior of changes in the spectra of NLS1 during variations in flux, on both short (1000 s) and long (months to years) time-scales indicate that the spectra become harder when the soft X-ray flux rises. This is interpreted as evidence of variability in the underlying hard X-ray power law continuum rather than changes in the soft X-ray spectral shape. The characteristics of the sample of NLS1s were compared to a sample of low redshift AGN with published ROSAT observations (the RC sample). A Kolmogorov-Smirnov test was performed on 44 properties of these two samples and it was found that the NLS1 sample had a significantly different distribution of Γ then the RC sample. The NLS1 sample does not show a significantly different distribution of Fe II emission line equivalent widths or [O III]:Hβ strengths from the RC sample, these properties are often quoted as being unusually strong or weak in NLS1s (respectively). The significant difference in the distribution of Fe II:Hβ between the samples is interpreted as due to the correlation of the equivalent width of Hβ with the FWHM of Hβ. We find that there is a significant difference in the 60μm and 100/μm luminosities between the two samples. We have extended the analysis of the soft X-ray properties of narrow-line AGN to include a preliminary study of a large sample of intermediate type Seyfert galaxies obtained from the ROSAT archive. We find that type 1.8 and 1.9 Seyfert galaxies show a variety of spectral behavior ranging from low luminosity thermal emission, most likely due to activity related to normal spiral galaxies, and power law continua in some cases absorbed by large columns of cold gas. The nature of the X-ray spectrum of intermediate type Seyfert galaxies was investigated further by studying ASCA observations of NGC 4388 and ESO 103-G35. Both AGN have strong Fe Kα emission lines and power law continua absorbed by cold gas with NH~=1023 cm-2 . We find no indication of a reflection continuum in the 2-10 keV spectra of these objects.