Arsenic (As) accumulation and toxicity in plants differs greatly among plant species and also among organs or tissues in the same plant.Therefore in order to understand As toxicity in plant tissues, it is necessary to study its forms and subcellular distribution.Subcellular distribution and As forms were investigated in a hydroponic culture using 2 different As tolerant tobacco (Nicotiana tabacum) genotypes ZY90 and FSMY.