The aim of this study was to assess comparatively the effects of cadmium on two different in vitro cell models, a cell line derived from proximal tubule renal cells (LLC-PK1) and haemocytes or blood cells of mussels ( Mytilus galloprovincialis). Cells were seeded in 96-well microplates and exposed in vitro to different concentrations of cadmium (CdCl 2) ranging from 10 to 2000 μ m for haemocytes and from 1 to 100 μ m for LLC-PK1 cells, added to the culture medium. After 24 h of exposure, different assays were performed on haemocytes: neutral red uptake, phagocytosis of neutral red-stained zymosan, XTT assay, activity of lysosomal acid phosphatase and demonstration of the actin cytoskeleton using TRITC-labeled phalloidin. Cell viability expressed as LC50 was 750 μ m when using the neutral red assay and 400 μ m with the XTT assay. The phagocytic ability and the activity of acid phosphatase increased significantly in cells treated with Cd in a non dose-dependent manner. Doses of Cd above 100 μ m caused disruption of the actin cytoskeleton. In LLC-PK1 cells, cell viability expressed as LC50 was found to be around 40 μ m when using the neutral red assay and 50–60 μ m with MTT and LDH assays, respectively. These results show that mussel haemocytes are in general more resistant to Cd exposure than LLC-PK1 cells. Furthermore, Cd appears to stimulate phagocytic and lysosomal activities in haemocytes in vitro.