Suspension-cultured tobacco cells (Nicotiana tabacum L. cv. Barley 21) were treated with 0.1 (control condition), 10, and 20 mm of boron (B). The histochemical observations revealed the deposition of suberin in the walls of the 10 and 20 mm B-treated cells. Lignin content and the amount of phenolics esterified to the polysaccharides of the walls of the 10 and 20 mm B-treated cells were also higher than those in the 0.1 mm of B. Lignosuberization of the 10 and 20 mm B-treated tobacco cells was accompanied by the increase in the activities of phenylalanine ammonia-lyase (PAL), tyrosine ammonia-lyase (TAL), peroxidase (PO), and polyphenol oxidase (PPO). In spite of the lignosuberization of tobacco cells after treatment with 10 and 20 mm of B, no significant reduction was observed in their viability, compared to those under the control conditions.