A method of reducing the loss for ultra-wideband filters with parallel coupled lines is presented. For wideband operations, tight coupling levels are required for the coupled lines of the filters. For microstrip parallel coupled lines, tight coupling levels are obtained with very narrow strip widths, which may lead to excessive ohmic loss. With the parallel coupled line miniaturization technique using capacitive loadings, the same tight coupling level can be obtained with relatively wider strip widths. Thus the technique not only miniaturizes the filter, but also provides a means to reduce the overall loss of ultrawideband filters. Both the simulated and experimental results are provided.