Three subscales of the "Science Motivation Questionnaire II" (SMQII; motivational components: career motivation, self-efficacy and self-determination), with 4 items each, were applied to a sample of 209 secondary school students to monitor the impact of a 3-hour structured inquiry lesson. Four testing points (before, immediately after, 6 and 12 weeks after) were applied. The modified SMQII was factor-analyzed at each testing cycle and the structure confirmed. Only self-determination was shown to be influenced by an inquiry course, while self-efficacy and career motivation did not. Only self-efficacy and career motivation were intercorrelated and also correlated with science subject grades and subsequent achievement. Implications for using the modified SMQII subscales for research and teaching in secondary school are discussed.