Autism is characterized by social deficits, communication abnormalities, repetitive behaviors and cognitive inflexibility. Prenatal exposure to infection and subsequent inflammatory responses has been implicated in the etiology of autism. The aim of the present study was to verify whether a single early prenatal exposure to lipopolysaccharide (LPS) represents an experimental model of autism. We prenatally exposed Wistar rats to LPS (100 μg/kg, intraperitoneally, on gestational day 9.5), which mimics infection by gram-negative bacteria, and evaluated the behavioral patterns associated with autism: (1) ultrasonic vocalization (communication) of the pups calling their mothers (total number and latency to the first vocalization); (2) play behavior (pinning, sniffing the partner, crawls over/under the other animal, partner mounting, following the partner, and locomotion); and (3) hit scores on T-maze spontaneous alternation test (learning and memory). Our results showed that rats prenatally exposed to LPS emitted fewer ultrasonic vocalizations, played less (reduced all social parameters) and visited the same arm that was blocked in the previous sessions of the T-maze, than their respective controls. In all the cases, the results were considered as significant if p < 0.05. Thus, our model of prenatal LPS exposure resulted in social deficits, communication abnormalities and cognitive inflexibility, i.e., autism-like effects. Moreover, we suggest the T-maze spontaneous alternation test as a tool to evaluate repetitive/restricted behavior in rat models of autism. FAPESP.