Introduction: The interstitial deletion of chromosome 1q is a disease of rare incidence, which might be heritary or caused by spontanous changes within the chromosome respectively. The phenotype in most cases is based on the loss of macrochromosomal material within the long arm of chromosome 1. The characteristics of this syndrome include pre- and postnatal growth retardation, severe psychomotor retardation, microbrachycephaly, sparse fine scalp hair and eyebrows, deformity of scull with cleft of lips and palate, scoliosis, small hands and feet hernias, genital defects, clinodactyly of the fifth fingers and campylodactyly. Other morphological characteristics that have been reported are mainly kidney and cardiac abnormities. The number of symptoms are related to the loss of genetic material. To our knowledge this is the first description of a patient with interstitial deletion of chromosome 1 (q23-q31). Patient: We report an eleven year old boy with interstitial deletion of chromosome 1 (q23-q31). In addition to the known sceletal, orofacial disorders, hypothrophia and retardation we discovered a unilateral high-graded and contralateral middle-graded hearing loss. Conclusion: In infants with chromosome 1q syndrome adequate diagnostic procedures have to be employed to unveil sensineural hearing losses that might be overseen because of mental retardation. In particular a brainstem electric response audiometry should be considered for early diagnosis and treatment of a possible hearing-loss.