Twenty-two cats with a problem of urine spraying in the home were enrolled onto a double-blinded placebo-controlled study designed to evaluate the efficacy of feline facial pheromone (FFP) delivered continuously into the atmosphere in the home through an electrically heated diffuser for controlling the problem. The cats were randomly assigned to treatment or control groups according to a predetermined schedule and later analysis suggested that there were no significant differences in the demographic characteristics of the two groups. Compared with a baseline week during which no treatment was given, the mean level of spraying was significantly lower in the treated group after four weeks, but not significantly lower in the control group. The baseline level of spraying and the treatment, but not the week of treatment, were significant predictors of the amount of spraying during the trial. However, only the type of treatment given was a significant factor in the occurrence of new marks. Linear regression analysis suggested that there was a significant relationship between the amount of spraying and the duration of the use of FFP.