The losses in typical LTCC interconnections at millimeter wave frequencies up to 110 GHz have been measured using FGCPW meander line test structures. The percentage contributions of conductor loss, dielectric loss and surface roughness loss have been analyzed and the significance of the conductor geometry, surface roughness and fabrication errors are evaluated. The relative permittivity and loss tangent for several LTCC samples are also presented over a range of millimeter wave frequencies