The survival times of 148 dogs treated for pituitary-dependent hyperadrenocorticism were studied using clinical records from 3 UK veterinary centers between 1998 and 2003. Of these animals, 123 (83.1%) were treated with trilostane, while 25 (16.9%) were treated with mitotane. Treatment groups were compared using t-tests and analysis of variance (or their nonparametric equivalents) and chi-square tests. Survival data were analyzed using Kaplan-Meier survival plots and Cox proportional hazard methods. There was no significant difference between the population attributes from each center or between treatment groups. The median survival time for animals treated with trilostane was 662 days (range 8-1,971) and for mitotane it was 708 days (range 33-1,399). There were no significant differences between the survival times for animals treated with trilostane and those treated with mitotane. In the multivariable model (including drug, center, breed group, weight, diagnostic group, and age at diagnosis), only age at diagnosis and weight were significantly negatively associated with survival. Importantly, there was no significant effect of drug choice on survival.