Many have called for reform of the science curriculum to incorporate the process of inquiry: this has been shown to improve student understanding of biological concepts. Laboratory activities provide excellent opportunities to incorporate inquiry in to the curriculum. This study used a modified version of the Laboratory Task Analysis Instrument (LAI) to analyse diffusion activities in 10 manuals available to two-year and four-year colleges in the United States. The analyses revealed that most manuals did not include much inquiry, similar to previous studies of high school laboratory manuals. Furthermore, they often failed to engage students in the planning and design of the activity, and they did not encourage students to apply what they learned in a broader context--two essential components of inquiry. This study showed the need for educators to review the materials that are available and implement changes that would promote the use of inquiry. (Contains 1 online reference and 2 tables.)