Chloroacetaldehyde (CAA) is a nephrotoxic metabolite of the antineoplastic agent ifosfamide and the putative cause for chronic ifosfamide-nephropathy, mostly presenting in proximal tubular dysfunction. Since CAA is a sulfhydryl-reagent, we tested if thiol proteases such as caspases -3, -8 and cathepsin B play a role in development of renal damage by CAA. CAA led to a potent inhibition of the cysteine proteases caspase-3, -8 and cathepsin B in hRPTEC. Due to inhibition of caspases, mostly necrotic cell death could be observed after CAA-exposure. Incubation with CAA increased the size of lysosomes, reflecting protein overload due to inhibition of cathepsin B. Furthermore, 48 h exposure to 150 mM CAA led to a 10-fold increase in collagen III. Conclusions: (i)) CAA enforces necrotic cell death by caspase-inhibition. (ii) CAA inhibits cathepsin B, leading to cellular protein overload. (iii) Induction of necrosis by CAA favours inflammatory events. (iv) Intracellular protein overload initiates proinflammatory and profibrotic signals, reflected by enhanced collagen III-synthesis. (v) Thus, necrosis due to caspase-inhibition and intracellular protein overload due to reduced cathepsin B-activity could mutually potentiate fibrosis and inflammation, finally resulting in tubulointerstitial fibrosis.