Growing demand to quantify the research output from public funding has tempted funding agencies, promotion committees and employers to treat numerical indices of research output more seriously. So many assessment exercises are now conducted worldwide that traditional peer assessment is threatened. Here, we describe a new citation-based index (Hirsh's h index) and examine several factors that might influence it for ecologists and evolutionary biologists, such as gender, country of residence, subdiscipline and total publication output. We suggest that h is not obviously superior to other indices that rely on citations and publication counts to assess research performance.