BACKGROUND: Difficulties in recognizing emotions and mental states are central characteristics of autism spectrum conditions (ASC). However, emotion recognition (ER) studies have focused mostly on recognition of the six 'basic' emotions, usually using still pictures of faces. METHODS: This study describes a new battery of tasks for testing recognition of nine complex emotions and mental states from video clips of faces and from voice recordings taken from the Mindreading DVD. This battery (the Cambridge Mindreading Face-Voice Battery for Children or CAM-C) was given to 30 high-functioning children with ASC, aged 8 to 11, and to 25 matched controls. RESULTS: The ASC group scored significantly lower than controls on complex ER from faces and voices. In particular, participants with ASC had difficulty with six out of nine complex emotions. Age was positively correlated with all task scores, and verbal IQ was correlated with scores in the voice task. CAM-C scores were negatively correlated with parent-reported level of autism spectrum symptoms. CONCLUSIONS: Children with ASC show deficits in recognition of complex emotions and mental states from both facial and vocal expressions. The CAM-C may be a useful test for endophenotypic studies of ASC and is one of the first to use dynamic stimuli as an assay to reveal the ER profile in ASC. It complements the adult version of the CAM Face-Voice Battery, thus providing opportunities for developmental assessment of social cognition in autism.