Background and Objectives: Adenoid cystic carcinoma of salivary glands is characterized by insidious growth over many years, local recurrences, and distant metastasis and classified to three distinct histologic subtypes: tubular, cribriform, and solid. The solid type is known to have the worst prognosis. However, histopathologic heterogeneity is observed in tumors from the same patient. We have attempted to elucidate the genotypic differences, characterized by polysomies of chromosome 17, in adenoid cystic carcinoma according to the phenotypic histopathologic heterogeneity. Materials and Methods: Fluorescence in situ hybridization was performed on formalin-fixed paraffin blocks from seven patients with head and neck adenoid cystic carcinoma, using the centromeric $alpha$-satellite probe of chromosome 17 to detect nuclei exhibiting polysomy. The difference in polysomeric chromosome expression in cribriform, tubular, solid type and type I, II, III according to the Szanto classification was analyzed. Results: Polysomy of chromosome 17 was found in 15.28% of the cribriform type, in 15.68% of the tubular type, and in 18.87% of the solid type. The proportion of polysomy was statistically higher in the solid type than in the cribriform type(p<0.05), and the proportion of polysomy increased progressively from type 1 to type 3, but this trend was statistically insignificant(p>0.05). Conclusion: We suggest that there may be genetic variations in tumor from the same patient depending on the histopathologic heterogenetiy in adenoid cystic carcinomas.