Severe pancytopenia associated with the use of alternating steroid with chlorambucil regimen was described in six patients with nephrotic syndrome secondary to lupus membranous nephropathy (WHO class V). We believe this is the first report describing the life-threatening degree of marrow toxicity associated with this regimen of alternating steroid with chlorambucil in a Chinese population. Our data suggests that the susceptibility to marrow toxicity with the use of chlorambucil may only be applicable to Chinese patients with underlying systemic lupus erythematosus as a similar degree of toxicity has neither been reported in lupus patients of other ethnic groups nor in non-lupus patients of Chinese origin.