This invention relates to certain 6-aryl-7-halo-imidazo[1,2-a]pyrimidines or pharmaceutically acceptable salts thereof, and compositions containing said compounds or pharmaceutically acceptable salts thereof, wherein said compounds are anti-cancer agents useful for the treatment of cancer in mammals by promotion of microtubule polymerization. This invention further relates to a method of treating or inhibiting the growth of cancerous tumor cells and associated diseases in a mammal and further provides a method for the treatment or prevention of cancerous tumors that express multiple drug resistance (MDR) or are resistant because of MDR, in a mammal in need thereof which method comprises administering to said mammal an effective amount of said compounds or pharmaceutically acceptable salts thereof.