The interaction of small cationic vesicles composed of dioctadecyldimethylammonium bromide (DODAB) with normal versus transformed mouse fibroblasts is described using cell microelectrophoresis, turbidimetry, and cell viability assays over a wide range of DODAB concentrations (10(-7)-10(-3) M). Normal and transformed cells (10(4) cells/mL) attain a point of zero charge at, respectively, 18.0 and 1.6 mu M DODAB. Further increasing DODAB concentration (C) generates positively charged cells. At 10(5) cells/ml and C greater than or equal to 50 mu M, DODAB induces cell-cell adhesion. For transformed and normal cells, peak adhesion occurs at 100 and 1000 mu M DODAB, respectively. Upon 0.5 h interaction time with 100 mu M DODAB, at 10(4) cells/mL, 20% of cell death is obtained for normal cells whereas transformed cells remain unaffected. Transformed cells have a higher affinity for DODAB vesicles than their normal counterparts but are more resistant to DODAB-induced cell death. The results indicate that DODAB vesicles interact with cells with very high affinity at low ionic strength and are not toxic below 1 mM, suggesting that they might successfully deliver oppositely charged proteins or DNA strands to cells. These results may be of importance for Liposome-mediated processes currently being used for drug or gene delivery to cells.