Substantial interactions between drifting carriers in a semiconductor and slow circuit waves on meander lines have been demonstrated for the first time. Electronic gains in the meander‐meander line signal of up to 40 dB/cm were obtained with Ge at 4.2°K. Although no net gain was achieved with respect to the ports of the meander lines due to the structure's high transmission loss of 20–30 dB, the results demonstrate the possibility of solid‐state slow‐wave amplification which has been the subject of many previous theoretical studies.