Two experiments explored the possibility that lesions of avian hyperstriatum, which disrupt reversal learning, might have that effect through a potentiation of the influence of proactive interference. Neither experiment found any evidence to suggest excessive interference in hyperstriatal pigeons, from preceding training on a position (or color) discrimination, on retention of a color (or position) discrimination, and this was true both after a short (30 min) and after a long (6 or 7 day) retention interval. There was, however, evidence of a disturbance, not easily interpreted, in retention following the lesions. There was also convincing evidence, from both experiments, for the disruption by hyperstriatal lesions not only of reversal learning but also of tasks not involving reversals, a disruption that suggests a general tendency to perseverate in hyperstriatal birds.