With the aim to determine the grade of intensification of the extraction process of biologically active substances (BAS) from tomato seeds under the action of ultrasonic cavitation the phenomena generated by ultrasound in liquid media were studied. Initiation of cavitation in the liquid medium induces sonocapillary effects (SCE), acoustic microflows, and sound pressure. The SCE accelerates the extraction of BAS from tomato seeds under the action of ultrasonic cavitation. Since it is dificult to study the SCE in the process of cavitation treatment of seeds by a high-speed imaging method, an indiresct method was used both for whole and milled seeds. The swelling index (SI) of the seeds was determined as described in the British Pharmacopoeia. For the experiments the seeds were milled; the particle dimensions amounted to 0.5 mm. The milled seeds were mixed with a certain portion of water and the suspension was treated under the action of ultrasonic oscillations at the following parameters: the frequency f = 22 kHz, amplitude ξ = 25 μm at a temperature within 50–55 oC. The swelling index was determined for untreated and ultrasonically treated seeds. The resuls are presented in Fig. 1. The action of ultrasonic cavitation intensifies the kinetics of the extraction process; in such a case, the most pronounced difference between the traditional and cavitational methods is obvious in the first 10-30 minutes. The difference can appear due to the absorbtion of the liquid in the membrane capillaries that promotes the solvent access in the capillaries of the material and increases the internal mass exchange in them. It was shown that the water holding capacity of the tomato seeds under the action of ultrasonic cavitation is by 80% greater than in the case of traditional method (Fig. 1). This confirms the fact that intensification of the solvent absorbtion in the membrane capillaries of seeds at the initiation of the cavitation treatment process makes a major contribution in the reduction of the process duration and in the increasing of the quantity of extracted BAS. Therefore, the sonocapillary effect is directly involved in the promotion of the mass exchange process inside membrane capillaries of the tomato seeds. It was shown that the sonocapillary effect generated due to the implosion of cavitation bubbles in the transverse section of the membrane capillaries in the treated material is the predominant factor that accelerates the extraction process of BAS, in this case, from the tomato seeds. At the action of ultrasonic cavitation the water holding capacity of tomato seeds is by 80 – 85 % greater than in the case of the traditional method.