The adsorption of cationic polyelectrolytes and cationic surfactants from aqueous solution onto silica substrates was examined using atomic force microscopy (AFM) in surface force mode and in surface imaging mode. The polymers were poly(diallyldimethylammonium chloride) (PDADMAC), poly-L-lysine hydrobromide, and polyvinylbenzyltrimethylammonium chloride, and the surfactants were hexadecyltrimethylammonium chloride (CTACl) and hexadecyltrimethylammonium bromide. CTACl forms micelles at the interface between micellar CTACl solutions and silica. These micelles desorbed when the CTACl solution was replaced with water. Am adsorbed layer of CTACl hindered adsorption of PDADMAC. This is because CTACl generates a surface change that has the same sign as the polymer. When PDADMAC adsorbed in the absence of CTACl, it formed a featureless, neutral layer. The PDADMAC did not desorb, even after extended rinsing with water. When an adsorbed layer of PDADMAC was exposed to CTACl solution above the critical micelle concentration, the AFM image and surface force are very similar to those observed when CTACl adsorbs to silica. This adsorbed layer is either spheres or hemispheres.