To study the agreement between three tests for aspiration, barium videofluoroscopy, salivagram, and milk scan we studied 63 children with severe non-ambulant spastic quadriplegic cerebral palsy (CP) aged 14 months to 16 years (32 males, 31 females). The salivagram was most frequently positive (56%, 95% confidence interval 43 to 68%); the next most frequently positive was barium videofluoroscopy when aspiration was defined as the presence of either laryngeal penetration of material or frank aspiration (39%, 95% confidence interval 26 to 53%). The milk scan was rarely positive (6%, 95% confidence interval 2 to 16%). Agreement between the tests of aspiration was poor. The maximum agreement (kappa=0.20) was between aspiration as diagnosed with the salivagram and by barium videofluoroscopy. Positive tests for aspiration are frequent in children with severe CP. Frequency varies widely depending on the investigation used. There is poor agreement between tests used for the diagnosis of aspiration. This information is of importance in assessing the significance of test results.