This paper presents a hypothesis on the importance of initial microbial adhesion in the overall process of biofilm formation. The hypothesis is based on the realization that dynamic shear conditions exist in many environments, such as in the oral cavity, or on rocks and ship hulls. Recognizing that an entire biofilm is detached during high shear once the bond between the initially adhering organisms and a surface (often constituted through a so-called 'conditioning film') is broken, it becomes clear that research should focus on detachment rather than adhesion. Experiments were done in a parallel plate flow chamber in which attempts were made to detach adhering oral streptococci from glass by applying a high shear caused by the passage of a bubble, giving an air-liquid interface. Detachment of streptococci from bare glass and from an initially adhering actinomycete strain appeared not to occur. However, substantial detachment of adhering streptococci occurred when adhesion was mediated through a salivary conditioning film, presumably because of cohesive failure in the conditioning film.