The aims of this study were twofold: first, to develop and validate a timed test of unimanual and bimanual dexterity suitable for those with disability affecting hand function; second, to explore relationships between unimanual and bimanual completion times. METHOD: We developed the Tyneside Pegboard Test (TPT), an electronically timed test with three peg sizes, incorporating an asymmetrical bimanual task. Nine hundred and seventy-four participants (455 males, 519 females; age range 4-80y) provided normative data. Test-retest reliability and construct validity were assessed (50 adults: 14 males, 36 females; 15-73y) on two occasions 2 weeks apart. Bimanual and unimanual completion times were measured in 87 children (51 males, 36 females) with unilateral cerebral palsy (CP) and 498 individuals in a comparison group (238 males, 260 females; 5-15y). RESULTS: The comparison group showed an asymmetrical U-shaped relationship between completion times and age. Intraclass correlation coefficients ranged from 0.74 to 0.91, indicating moderate test-retest reliability. There was a negative relationship between average TPT bimanual times and Purdue pegboard bimanual scores (Spearman's rho -0.611, degrees of freedom 44, p<0.001). Children with unilateral CP had greater prolongation of bimanual than unimanual completion times compared with the comparison group (mean difference 20.31s, 95% confidence interval 18.13-22.49, p<0.001). INTERPRETATION: The TPT is accessible for those with impaired hand function. Children with unilateral CP demonstrated disproportionate bimanual deficits, even allowing for unimanual dexterity: this has implications for therapy. WHAT THIS PAPER ADDS: We developed an adapted, electronically timed 9-hole pegboard test. Our modifications facilitate use by those with disability affecting hand function. The test incorporates an asymmetrical bimanual task. Children with unilateral cerebral palsy showed disproportionate bimanual dexterity deficits even allowing for unimanual dexterity. CI - (c) 2017 The Authors. Developmental Medicine & Child Neurology published by John Wiley & Sons Ltd on behalf of Mac Keith Press.