Based on field data, this study presents the growth curve of Balloniscus glaber Araujo & Zardo, 1995, a terrestrial isopod species found in Parque Estadual de Itapuã (PEI), Rio Grande do Sul, Brazil. Specimens were monthly sampled, from May 2004 to April 2005, at PEI. Captured individuals were sexed, their cephalothorax width was measured, and the growth curve was described according to von Bertalanffy's model. Male and female growth curves are described by the equations: Wt = 2.256[1-e-0.00394(t+91.128)] and Wt = 2.588[1-e-0.00301(t+101)], respectively. Curves show differential growth between males and females, with females reaching higher W<FONT FACE=Symbol>¥</FONT>, and a slower growth rate than males. Based on theses curves, life span was estimated.