Introduction: The objective of the study was to determine the factors independently related with the development of castration resistance (CR) in prostate cancer (PC) in the medium term. Material and methods: 155 patients diagnosed with metastatic PC with a follow-up of up to 39 months. Data taken from the National PC Registry. The evaluated variables were age, PSA, nadir PSA, Gleason, perineural invasion, TNM stages, and ADT type (intermittent/continuous). Results: Mean follow-up 26,2 +/- 13,4 months. 47.1% developed early CR, with mean time until onset of 12,2 8,7 months. Univariate analysis the mean PSA was correlated with CR (290 +/- 905,1 ng/mL in non CR, 519,1 +/- 1437,2 ng/mL in CR, P < .001), mean age (73,3 +/- 8,3 years in non CR, 69,1 +/- 9,3 in CR P = .01), mean PSA nadir (15,5 +/- 57,3 ng/mL in non CR, 15,9 +/- 23,7 ng/mL in CR, p < 0,001), Gleason (in >= 8, HR:2,11. 95% CI: 1.22-3.65, p = 0.006), and T stage (in T3-T4, HR: 2.85. 95% CI: 1.57-5.19, P < .001). Multivariate analysis the independent variables associated to CR are age (HR: 0.96. 95% CI: 0.94-0.99, P = .01), PSA nadir (HR: 1.65. 95% CI: 1,43-1,91, P < .001), and T3-T4 stage (HR: 2.11. 95% CI: 1.10-4.04, P = .02). Conclusions: PSA nadir and T3-T4 tumor stage at diagnosis are associated to an increased risk of developing CR. In addition, age at diagnosis is shown as a variable that decreases risk. Therefore, an older age would be associated with lower risk probability of CR in the medium term. (C) 2019 AEU. Published by Elsevier Espana, S.L.U. All rights reserved.