Time-of-Flight Secondary Ion Mass Spectrometry is nowadays intensively used for polymer surface characterization. The fingerprint nature of ToF-SIMS spectra acquired in static conditions is now well established. Characteristic molecular fragment ions can be used for identification of polymer and organic materials present at the surface. The aim of this presentation is to discuss some issues related to surface quantification with this technique. This is of special importance for applications where copolymers and polymer blends are involved. First, we will discuss the use of end group ToF-SIMS signals. Our recent results obtained on monodisperse polystyrene samples show that ToF-SIMS is very sensitive to end groups. Their intensity can be used, after appropriate calibration, to quantify molecular weight at the surface. Some end groups (sec-butyl) are seen to influence also the intensity of main chain fragments. This is due to a specific interaction with the first neighboring repeat unit. It consists in a mechanism of H transfer, with no long-range (intermolecular) influence. So, the end group signals allowed us to quantify the surface composition of polystyrene blends with close molecular weights but different end groups. Second, we will discuss the use of characteristic fragment intensity and intensity ratios for blend and copolymer surface quantification. For polystryrene / poly (2,6-dimethyl-1,4-phenylene oxide) blends, which are miscible and do not exhibit any surface segregation, the intensity of the characteristic ions is seen proportional to homopolymer bulk concentration, allowing a staighforward surface quantification. But for random copolymers, different situations are observed. For random styrene butadiene rubbers, an appropriate choice of ions leads to "bulk like" surface composition, as expected. However, styrene / methyl methacrylate random copolymers, exhibit strong matrix effects due to a specific interaction between adjacent species taking place during the secondary ion emission. This outlines the need of understanding the fragmentation pathways in order to use ToF-SIMS intensities for surface quantification. Another approach would be the use of "full spectrum" chemometrics multivariate methods.