The present French-German cooperative study focusses on the genotype-phenotype relationship of mutations of the FMR-1 gene and psychiatric conditions in mothers with a full mutation in the FMR-1 gene of fra-X children (n = 13), mothers with a premutation in the FMR-1 gene of fra-X children (n = 61), as well as premutated siblings of these mothers without affected children (n = 17) and two nonmutated control groups: 1) siblings of these mothers with normal CGG repeat (n = 18) and 2) mothers of non-fra-X autistic children (n = 42). Mothers with a full mutation in the FMR-1 gene and mothers with a premutation in the FMR-1 gene did not differ in frequency of any axis I disorder. However, both groups obtained more often the diagnosis of social phobia in comparison to the control group of mothers of autistic children. Moreover, mothers with a premutation in the FMR-1 gene of fra-X children and their siblings with the premutation (without affected offspring) revealed a similar frequency of social phobia. Furthermore, avoidant personality disorder (PD) was more common in groups of carriers of the full and premutation than in siblings without mutation or the control group of mothers with autistic children. On the basis of our data, we therefore suggest that social avoidance (expressed as social phobia or avoidant PD) has been underestimated in previous studies of carriers with the FMR-1 full or premutation. Comorbidity of axis I and axis II psychiatric diagnoses was mainly restricted to the group of carriers of the full mutation and carriers of the premutation of FMR-1. Correlations between size of CGG repeat and IQ as well as CGG and age of onset of axis I diagnosis were nonsignificant. IQ of subjects had no impact on the presence or absence of axis I and/or axis II diagnoses.