This paper describes the characteristics and application of lumped double crosstie slow-wave transmission lines (DCT-SLWs) which we previously proposed. Firstly, the relationship between the DCT-SLW's characteristics and their parameters, i. e. triplate stripline widths and inductor resistances, are numerically and experimentally investigated. Excellent slow-wave lines with both high slow-wave factors (1240) and a wide characteristic impedance range (35100Ω) are achieved in good agreement with calculated results. A 50-Ω DCT-SLW that reduces circuit area more than 80%, and has an insertion loss less than that of 22-µm-wide TFMS lines is achieved by adapting a low-loss inductor in the frequencies below 14.5 GHz. Secondly, the application of DCT-SLW to non-dispersive, dispersive delay lines and branch-line hybrids is discussed. Specifically, very small 4-GHz-band branch-line hybrids are fabricated in a chip area of 0.7 mm2. Fundamental microwave circuits utilizing slow-wave lines in MMICs are demonstrated for the first time.