We examined variation in calls and calling behavior in two populations of Bufo valliceps in south-central Texas. Both pulse rate of advertisement calls and call rate were positively related to body temperature, whereas call duration was negatively correlated with body temperature. Advertisement call frequency was not significantly correlated with toad temperature, but was negatively correlated with SVL. Of the temporal advertisement call variables, only call duration was significantly correlated (positively) with SVL. Release call frequency was negatively correlated with SVL. Field observations revealed significantly greater variation among than within males for call rate, call duration, and calling effort. However, despite the consistency of individual calling behavior, calling activity varied with social context. Calling effort was weakly, positively correlated with male density. Call rate and calling effort varied nonlinearly with nearest neighbor distance. Both variables were highest at intermediate distances (2.5-7.5 m), decreasing as nearest neighbors became very close (<2.5 m) and very distant (>7.5 m).