The aim of this study was the development of a method for the determination of 12 urinary monohydroxy metabolites of PAHs, namely 1-hydroxynaphthalene, 2-hydroxynaphthalene, 2-hydroxyfluorene, 9-hydroxyfluorene, 1-hydroxyphenanthrene, 2-hydroxyphenanthrene, 3-hydroxyphenanthrene, 4-hydroxyphenanthrene, 9-hydroxyphenanthrene, 1-hydroxypyrene, 6-hydroxychrysene, and 3-hydroxybenzo[a]pyrene. Analytes were determined in the presence of deuterated analogues as internal standards, by GC/MS operating in the electron impact mode. Sample preparation was performed by enzymatic hydrolysis of glucoronate and sulphate conjugates of hydroxy metabolites of PAHs, liquid-liquid extraction with n-hexane, and derivatization with a silylating reagent. The method is very specific, limits of quantification are in the range 0.1-1.4 microg/l, and range of linearity is from limit of detection to 208 microg/l. Within- and between-run precision, expressed as coefficient of variation, are <20%; accuracy for most analytes is within 20% of the theoretical value. An application of the proposed method to the analysis of 10 urine samples from coke-oven workers shows that 1-hydroxynaphthalene and 2-hydroxyfluorene were the most abundant compounds (median 61.4 and 69.7 microg/l, respectively), while 6-hydroxychrysene, and 3-hydroxybenzo[a]pyrene were always below the quantification limit.