The aim of the study was to investigate the effect of a physical fitness intervention program within a physical education class on selected health-related fitness components among Malaysian secondary school girls. A quasi-experimental design was adopted for the study. Two schools in a district were randomly selected. In each school, two classes were randomly assigned intact to the experimental group (n = 48), and the other was the control group (n = 38). Pretest data were collected on cardiovascular endurance, flexibility and muscular strength. The experimental and the control groups underwent regular physical education classes twice a week for ten weeks. Apart from the regular physical education classes, the experimental group underwent the treatment of four exercises in form of a circuit immediately after the warm-up session. After ten weeks, posttest data were collected. ANCOVA indicated that there was a main effect in cardiovascular endurance F (1, 83) = 44.69, p < .05 and for flexibility F(1,83) = 46.80, p < .05. As for muscular strength, the result was not significant F (1,83) = 3.54, p>.05. The results indicate that a ten-week physical fitness program within the physical education class was effective in enhancing cardiovascular endurance and flexibility among Malaysian secondary school girls.Key words: cardiovascular endurance; flexibility; muscle strength; physical inactivity; secondary school girls.---Sažetak Cilj ovoga istraživanja bio je proučiti utjecaj programa interventnog vježbanja u nastavi tjelesnog odgoja na određene komponente zdravstvene-tjelesne spremnosti među srednjoškolkama u Maleziji. U istraživanju smo se koristili kvazieksperimentalnom metodom.  Istraživanje je obuhvatilo dvije nasumce odabrane škole u okrugu. U svakoj su školi nasumce odabrana dva cjelokupna razreda od kojih je jedan razred označen kao eksperimentalna skupina (n = 48), a drugi kao kontrolna skupina (n = 38). Predtestom su dobiveni podaci vezani uz kardiovaskularnu izdržljivost, fleksibilnost i mišićnu snagu. Eksperimentalna i kontrolna skupina bile su deset tjedana podvrgnute redovnoj nastavi tjelesnog odgoja dva puta tjedno. Uz redovnu nastavu tjelesnog odgoja eksperimentalna skupina bila je podvrgnuta tretmanu od četiri vježbe po stanicama u krugu odmah nakon uvodnog dijela sata – zagrijavanja. Nakon deset tjedana dobiveni su rezultati posttesta. ANCOVA je pokazala da su posljedice vidljive u kardiovaskularnoj izdržljivosti F(1, 83) = 44,69, p < ,05 i fleksibilnosti F(1,83) = 46,80, p < ,05. Što se tiče mišićne snage, rezultat nije bio značajan F(1,83) = 3,54, p> ,05. Rezultati ukazuju na to da je 10-tjedni program interventnog vježbanja u redovitoj nastavi tjelesnog odgoja pridonio poboljšanju kardiovaskularne izdržljivosti i fleksibilnosti među malezijskim srednjoškolkama.Ključne riječi: kardiovaskularna izdržljivost; fleksibilnost; mišićna snaga; fizička izdržljivost; srednjoškolke