Abstract: One way female plethodontid salamanders provide parental care is through the prevention of desiccation. In addition to direct parental care, offspring survival can be influenced by the choice of oviposition site and the environmental factors associated with that site. To provide further support for the idea that available moisture is the dominant factor associated with egg size and survival, we conducted a field survey to examine the relationship between oviposition site characteristics and reproductive success in red-backed salamanders, Plethodon cinereus . In addition, we manipulated moisture conditions in mesocosms, and measured the effect of moisture on brooding females and their eggs. We found female snout-vent length to be positively correlated with soil moisture, cover object size, humidity and egg survival. Humidity was also positively correlated with egg volume. This study supports the idea that soil moisture and humidity are the primary environmental parameters that are most conducive to reproductive success in terrestrial salamanders. Females contribute greatly to egg number and size through both pre-oviposition and post-oviposition behaviors, and it is clear that larger mothers increase their reproductive fitness by ensuring a moist and humid environment for the successful development of her eggs.