Tricritical behavior, in particular, equations of state, critical exponents (δ, β) for the dimension d ≪ 3σ/2 (σ: potential-range parameter, 1 ≪ σ≤2) and logarithmic corrections in d = 3σ/2, of classical N-component spin systems with a short-range or long-range interactions is studied by means of the renormalization theory. The results obtained for the long-range interactions are new and show to be more classical than those of the ordinary phase transitions.