Measured values of electron density at 600 km altitude obtained from the Japanese Hinotori Satellite during February 1981–June 1982 are used to assess the predictability of the International Reference Ionosphere (IRI) within ±25° geomagnetic latitude along 75°E meridian. The observed and IRI predicted data pertains to moderate ( F 10.7≈164) and high ( F 10.7≈238) solar activity levels. Results show that the measured daytime electron density is higher than those predicted by the IRI in all seasons and latitudes during moderate solar activity. The difference between prediction and observation could be as high as 100% depending on location, local time and season. The underestimation of observed density by the model reduces to some extent during solar maximum. Nighttime density predicted by the IRI matches well with observations.