We present the infrared spectra of Herbig Ae/Be stars including the Infrared Space Ob-servatory (ISO) data. To investigate the overall properties of their circumstellar dust envelope and/or disk, we combine the IR spectra with photometric data ranging from the UV through the optical into the sub-mm region. We study the general characteristics of the spectral energy distributions using simple analysis. We plot the positions on the HR-diagram to compare with the theoretical pre-main-sequence evolution tracks.