The weldabilities of polyamide 6 (PA-6), polyamide 6,6 (PA-6,6), 33 wt% glass-filled PA-6,6 (33-GF-PA-6,6), and amorphous polyamide (PA-A) are assessed through 120 Hz vibration welds. Weld strengths equal to those of the base resins can easily be obtained in vibration welds of both undried and dried PA-6 and PA-6,6. Relative weld strengths in the range of 54-57% are demonstrated for 120 Hz welds of 33-GF-PA-6,6. Relative weld strengths in the range of 90-97% are demonstrated for dried PA-A. The highest relative weld strengths obtained in hot-tool welds of undried and dried PA-6,6 are only 57% and 54%, respectively.