Antimicrotubule agents paclitaxel, docetaxel and vincristine are used in treatment of breast cancer. They bind to beta-tubulin subunit of microtubules. Multidrug resistance developed against these drugs remains a serious clinical problem. Different beta-tubulin izotypes possess differential assembly/disassembly dynamics. In this study, expressions of beta-tubulin isotypes, and mutations in TUBE gene were investigated in paclitaxel, docetaxel and vincristine resistant MCF-7 breast carcinoma cell lines. Resistant sublines were developed in the laboratory by continuous drug applications in dose increments and development of resistance were assayed by cytotoxicity analysis. Gene expression levels of beta-tubulin isotypes were investigated by RT-PCR. Exon 4 of the TUBB gene was amplified by PCR and the products were sequenced for determination of mutations. According to expression analysis, mRNA levels of beta II-, beta III- and beta V-tubulin isotypes were significantly upregulated in paclitaxel and docetaxel resistant cells where they were significantly downregulated in vincristine resistant cells. Sequence analysis of exon 4 of TUBB gene coding for beta I-tubulin revealed that MCF-7/120nMDoc cells carry Gln-327 -> His mutation and MCF-7/120nMVinc cells have His-179 -> Pro mutation. In conclusion, differential expression levels of beta II-, beta III- and beta V-tubulin isotypes and mutations in TUBB gene were determined in paclitaxel, docetaxel and vincristine resistant MCF-7 cells. It was shown for the first time that beta V-tubulin expression level may be correlated to resistance to antimicrotubule drugs. Though more functional analysis is required, the data presented here provides an insight into mechanisms of paclitaxel, docetaxel and vincristine resistance through alterations in tubulin/microtubule system.