In this literature review the methods using ultrasounds in basic polymer processing - injection molding and extrusion - were presented. Two basic variants of such measurements were characterized, namely echo method using one transducer and the transmission method using two transducers, placed at opposite sides of the system investigated. The possibilities of transmission method application for the measurements in the injection nozzle (Fig. 1) and echo method application in the mold cavity during processing (Fig. 2) were discussed. Ultrasonic transducers let obtain the data necessary for controlling the process of producing of the fittings showing required properties. As well the possibilities of ultrasounds use during extrusion, by application of ultrasonic transducers connected with buffer rods (Fig. 3 and 5) were presented. Results of investigations and the estimation of quality of joint between two layers obtained in co-extrusion were given and interpreted (Fig. 4).