PEI coating promotes firm attachment of weakly anchoring cells to the substratum. The loss of cells induced by a protocol that involved multiple washings was measured to assess the strength in the attachment of cells to culture dishes coated with factors that promote cell anchoring. PEI was compared to other attachment factors (collagen, PDL) and to untreated control dishes. The relative cell counts were normalized by assigning an arbitrary value of 100.0% to the PEI-pretreated dishes. PEI coating resulted in significant enhancement of anchoring strength in PC-12 cells (graph A) and in HEK-293 cells (graph B), comparing favorably to other commonly used attachment factors. No benefits were observed in the attachment of a strongly anchoring cell line (MYS cells, graph C). The bars show the average ± standard deviation of triplicate assays, which are representative of at least three different experiments performed (* significantly higher than untreated control, p < 0.01; ** significantly higher than untreated control in the experiment presented, p < 0.01, but significance not maintained in independent experiments).