Epidemiological studies show a higher point prevalence of posttraumatic stress disorder (PTSD) in women than in men, and early evidence has suggested that gender may moderate hippocampal volume deficits in PTSD. Our objective was to use random-effects meta-regression to assess gender effects on hippocampal volume deficits in PTSD. Using the terms posttraumatic stress disorder, gender, MRI, hippocampus, trauma, and abuse, we searched electronic databases for peer-reviewed articles up to April 2009 containing data for hippocampal volume and gender composition in PTSD adults compared with controls. We identified 23 studies that met inclusion criteria and calculated effect sizes for differences in hippocampal mean volumes for each study and used the percentage of men with PTSD as a continuous moderating variable in meta-regression. Additionally, we did a subgroup analysis of hippocampal volume deficits between women and men with gender as a categorical moderating variable. Hippocampal volumes were significantly smaller in the PTSD group compared to the control group, but gender did not significantly moderate any effect sizes in the meta-regression or subgroup analyses. The lack of gender moderation on hippocampal volume deficits suggests that hippocampal volume deficits in PTSD are independent of gender. The higher prevalence of PTSD in females than in males does not correspond to increased hippocampal volume deficits in women with PTSD compared to men with PTSD, and neither gender appears protective against hippocampal volume deficits in adults with PTSD. © 2011 Wiley-Liss, Inc.