By 1968, the priority of bringing modern mathematics ideas to all post-primary students was the focus of Portuguese reform. In the two branches of secondary education—liceus and technical schools, mathematical curricula changed between 1967 and 1970. Two textbooks were published for the 1st grade of secondary education, one for liceus and one for technical schools. Performing a textbook analysis on these books allowed an insight into the curriculum presented to teachers in each branch. We focused the analysis on integers. Investigation showed that the approaches used to introduce integers and their operations were very different. There is mathematical consistency and coherence within each textbook. Throughout the text they both ask for students’ attention and participation, using simple speech and mathematical day-life applications. However, there are few exercises and activities to assist students’ acquisition of knowledge, as well as no diagnostic tests that allow the verification of that knowledge.