This article describes a 13-week laboratory course called Human Toxicology taught at the University of Otago, New Zealand. This course used a guided inquiry based laboratory coupled with formative assessment and collaborative learning to develop in undergraduate students the skills of problem solving/critical thinking, data interpretation and written discussion of results. The laboratory practices were a guided inquiry based around retinol's ability to potentiate acetaminophen-mediated hepatotoxicity. To induce critical thinking, students were given a choice as to which assay they could use to determine how retinol affected acetaminophen hepatotoxicity. Short summaries were handed in following each assay and formed the bases of the formative assessment. To complete the feedback loop, a summative assessment that consisted of all the graphs and concepts from the short summaries were combined into a manuscript. To give the students exposure to science communication, the manuscript had to be written in accordance to the submission guidelines for Toxicological Sciences. Evaluation of this course was determined by a student questionnaire using a Likert scale and students' responses were very favorable. While the subject matter was toxicological centric, the content could be easily modified to suit another subject matter in biochemistry and molecular biology. (Contains 3 tables and 5 figures.)