The factors influencing the habitat requirements and dispersal of juvenile Unionidae (unionids) between post-larval detachment from a fish host and burrowing into the substratum are largely unknown, although bed shear stress (τ_w) has been proposed as a critical factor. We used a laboratory wall jet apparatus to manipulate τ_w experimentally to examine the suspension and burrowing of juvenile Epioblasma triquetra, Villosa iris, Lampsilis fasciola, and Ligumia nasuta. τ_w and unionid suspension were significantly related when τ_w > 0.26 Pa, but this relationship also was influenced by mussel behavior. Greater τ_w was required for suspension when a mussel's foot adhered to a surface. Laboratory experiments confirmed predictions that juvenile unionids cannot become established when τ_w exceeds a critical value. Hydrodynamics and behavior strongly affect dispersal by juvenile mussels and may influence juvenile mussel habitat requirements, and thereby have implications for conservation efforts.