Myocardial interstitial fibrosis is a constant pathological finding in structural heart diseases of various etiologies that evolve with heart failure. Although fibrosis facilitates heart failure progression, until now no therapeutic strategy has been developed that ensures its reversal. A possible explanation for this may lie in the vision of myocardial interstitial fibrosis as a homogeneous lesion instead of a heterogeneous lesion in which different phenotypes can be distinguished using appropriate criteria. In addition, the notion that the heterogeneity of myocardial interstitial fibrosis may be cardiac disease-specific must be also considered when approaching this entity. Therefore, we propose that myocardial interstitial fibrosis represents a true challenge for transitioning from usual care to biomarker-based personalized treatment and precision medicine in heart failure. As a proof-of-concept, in this review we discuss the phenotyping of myocardial interstitial fibrosis in patients with heart failure attributable to hypertensive heart disease based on its histomolecular alterations and provide evidence of the prognostic relevance of the resulting stratification. Furthermore, we discuss the available information on some circulating biomarkers and certain pharmacological agents useful for noninvasive identification and personalized treatment, respectively, of those phenotypes. (C) 2019 Sociedad Espanola de Cardiologia. Published by Elsevier Espana, S.L.U.