Despite a rise in the use of handheld computers in classrooms, meaningful learning with personal digital assistant (PDA) technology remains poorly studied. This article reports results from an evaluation of customized handheld data collection software, the BioKIDS Sequence, which was used during an 8-week biodiversity curriculum unit by 5th and 6th grade students in southeastern Michigan. The article provides new information on design decisions and usability of our customized software; discuss learner use and preferences; and report rates of data accuracy. Most students were able to enter simple animal observations using an icon-driven, largely linear interface. The interface helped expand the types of data students were aware of, and allowed them to view and review their entries and flag them as uncertain, factors important in supporting accurate data collection. Other BioKIDS research indicates students were subsequently able to see simple patterns in their data to guide the formulation of future hypotheses, questions, or conclusions. The BioKIDS Sequence and PDA technology therefore represent a meaningful use of technology to support scientific reasoning.