A study was undertaken to investigate which of ten constructions are available to children of various ages for expressing conditionality. A modified sentence completion test based on use of the ten constructions was designed, field-tested, and administered individually to 20 students in each of five grades: kindergarten and grades two, four, six, and eight. Analysis of the data indicated that increasing numbers of constructions were available to subjects as they matured and that there was an observable developmental order among the ten constructions. Among the conclusions reached were that children as young as five years old have the ability to use a variety of linguistic means for expressing conditionality and that constructions involving "unless" were significantly more difficult than other constructions. (The paper includes numerous tables of data, a discussion of considerations in selecting a data collection method for the study, and a copy of the sentence completion test that was used.) (GT)