Quartz MicroBalance (QMB) system was implemented in the inner divertor region of JET in order to measure in situ and time resolved (0.1 sec) material fluxes (mainly carbon) and layer deposition. The system has been developed to operate at temperatures up to 200oC. The aim is to investigate carbon transport to the remote areas, and hence the tritium retention in dependence on plasma conditions. This question is still a major concern for the ITER operation. The mass sensitivity of the system is Sm = 7.5¥10 - 9g/Hz cm2. First reliable measurements were made during the C5 campaign (March ­ May 2002; 1000 plasma discharges). The results presented are based on 74 selected exposures under various conditions (strike point positions, input power, gas fuelling, ELM frequency). Most influencing to the carbon flux seems to be the position of the strike zone. In the average a yield of 1.9¥10-4 C-atoms have been deposited related to the D+ flux into the inner divertor.