The paper describes the results of total electron content ( N t ) derived from Faraday rotation of beacon signals from S66 satellites at Ahmedabad (23°01'N, 72°36'E) for the period November 1964 to April 1969. The daily variations of N t and of maximum electron density, N max, for any season are found to be similar; both showing a minimum at 05 hr and having a broad maximum around 14–16 hr. The range of N t , i.e. the ratio of maximum to the minimum value, is 15–20 for any of the seasons of low sunspot years. With increasing solar activity, there is almost no change in the annual range for the winter months, while the range during summer months decreases with increasing solar activity. The daily variation of the slab-thickness (τ) shows generally a midday maximum. A predawn peak of τ is also evident in winter months. A comparison of the N t values at Ahmedabad, Hyderabad and Delhi shows that at any of the stations, the daily minimum value of N t is highest in summer and least during winter; Ahmedabad values being slightly greater than the values at Delhi. The midday values of N t at any of the places show two equinoxial peaks within a year. For any particular month, the day-time N t value is highest at Ahmedabad which is known to be near the crest of the equatorial anomaly. The solar cycle variation of the daily maximum and minimum values of N t as well as daytime and night-time average values of τ are described for each season of the year.