Purpose: To document the development of a new parent- and day care-administered screening instrument (the Screening Instrument for 3-Year-Olds [SI-3]) to be used in a newly implemented, educationally motivated population language screening in Denmark. The authors investigated whether the basic principles of the SI-3 were working satisfactorily and studied the acceptability of the instrument. Method: To examine the general properties of the SI-3, 517 children froma populationbased sample were screened with the SI-3 instrument, which assesses various receptive and productive language dimensions on the basis of parental checklists and day care staff-administered structured tests. To examine the acceptability of the SI-3, 2 questionnaires were administered and completed by 291 parents and 135 preschool teachers. Result: We obtained a distribution with sufficient negative skew to differentiate among children with low scores, and the instrument displayed acceptable psychometric properties for most subscales. Results of the acceptability study suggest that the acceptability of the SI-3 is high among parents and day care staff, which supports a high attendance rate. Conclusion: The SI-3 captures a variety of language skills and is good at differentiating children in the lower end of the tail; it is thereby suitable for population language screening, although results indicated the need for some revision.