The aim of this study was to determine whether behavioural indicators such as marking frequency and whether cortisol/creatinine ratio (C/Cr) are influenced by three socialization sessions. Six adult shelter dogs were selected: Group 1 (n.3) with adequate social experience and Group 2 with behavioural problems of aggression against humans (n.2) and excessive fear response towards conspecifics (n.1). Spontaneous urine samples were collected for C/Cr after socialization sessions. C/Cr was positively correlated with urinary marking frequency (P<0.01) and negatively with faecal marking frequency (P<0.05). The correlation with urinary marking could be related to increased release of aldosterone under ACTH stimulus or to chemical information that dogs are in a stressful situation. The negative correlation with frequency of faecal marking could be related to inhibition of act in a novel situation as stress effect. Non-invasive monitoring for detection of cortisol could be useful to assess canine behaviour modulation following intraspecific socialization sessions.