A total of 163 echocardiographic studies on western lowland gorillas (Gorilla gorilla gorilla) were submitted for evaluation; 140 from 99 animals were suitable for analysis. Of these, 81 studies (42 studies from 35 males ranging in age from 11–41 yr and 39 studies from 31 females ranging in age from 11–41 yr) are reported here. Three studies from 3 females and 56 studies from 30 males were excluded from this report due to cardiac abnormalities. Cardiac parameters measured were aortic root (Ao Rt) diameter and left atrial (L atrium) size. Left ventricular (LV) measurements included left ventricular internal diameter in systole (LVID_s) and diastole (LVID_d) as well as diastolic septal (IVS) and posterior wall thickness (LVPW). Values considered to be normal in females >11 yr of age were: Ao Rt < 3.5 cm, L atrium < 4.0 cm, LVID_d < 5.0 cm, IVS < 1.4 cm, LVPW < 1.4 cm, and ejection fraction (EF) >60%. The data from male gorillas show a separation in animals based on three cardiac parameters: systolic function, LV cavity size, and LV wall thickness. Male gorillas >11 yr of age fall into two groups; unaffected and affected. Unaffected animals are defined as those with no echocardiographic abnormalities and a consistent Ao Rt of <4.0 cm, LVID_d of <6.0 cm, IVS and LVPW of <1.5 cm, and an EF of >58%. The affected group consisted of male gorillas that exhibited changes in echocardiographic parameters representing the presence of cardiovascular disease. The results determined in this database, gathered from data collected from 1999–2009, suggest a sex-based difference between males and females with predominantly males demonstrating evidence of cardiac disease. The most striking finding seen in this study is that of progressive LV hypertrophy and depressed LV EF in affected adult male gorillas.