The object of this study was to investigate the potential association of infections, especially group A hemolytic streptococcal infection, with the abrupt onset/exacerbation of tics or obsessive-compulsive behaviors. A structured clinical interview was used to evaluate 80 consecutive children, 5-17 years of age, with a diagnosis of tic disorder. Forty-two patients (53%) described a sudden, explosive onset or worsening of tic symptoms; 15 of these 42 had their exacerbation historically associated with an infection, nine of the 15 specifically with a streptococcal infection. Comparisons between those nine individuals and the remainder of the study population are presented. The results of this study reveal that descriptions of an abrupt tic onset or exacerbation are not uncommon in children with tic disorders; approximately 11% of children with tic disorders described abrupt changes of tic behavior within a 6-week period after a streptococcal infection.