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The industrial, scientific and medical (ISM) radio bands were originally reserved internationally for the use of RF electromagnetic fields for industrial, scientific and medical purposes other than communications. In general, communications equipment must accept any interference generated by ISM equipment

The ISM bands are defined by the ITU-R in 5.138, 5.150, and 5.280 of the Radio Regulations. Individual countries' use of the bands designated in these sections may differ due to variations in national radio regulations. Because communication devices using the ISM bands must tolerate any interference from ISM equipment, these bands are typically given over to uses intended for unlicensed operation, since unlicensed operation typically needs to be tolerant of interference from other devices anyway. In the United States of America ISM uses of the ISM bands are governed by Part 18 of the FCC rules, while Part 15 Subpart B contains the rules for unlicensed communication devices, even those that use the ISM frequencies. Thus, designers of equipment for use in the United States in the ISM bands should be familiar with the relevant portions of both Part 18 and Part 15 Subpart B of the FCC Rules.

The ISM bands defined by the ITU-R are (bands in italics are subject to local acceptance):

• 6.765–6.795 MHz (centre frequency 6.780 MHz)
• 13.553–13.567 MHz (centre frequency 13.560 MHz)
• 26.957–27.283 MHz (centre frequency 27.120 MHz)
• 40.66–40.70 MHz (centre frequency 40.68 MHz)
• 433.05–434.79 MHz (centre frequency 433.92 MHz) in Region 1
• 902–928 MHz (centre frequency 915 MHz) in Region 2
• 2.400–2.500 GHz (centre frequency 2.450 GHz)
• 5.725–5.875 GHz (centre frequency 5.800 GHz)
• 24–24.25 GHz (centre frequency 24.125 GHz)
• 61–61.5 GHz (centre frequency 61.25 GHz)
• 122–123 GHz (centre frequency 122.5 GHz)
• 244–246 GHz (centre frequency 245 GHz)

For many people, the most commonly encountered ISM device is the home microwave oven operating at 2.45 GHz. However, in recent years these bands have also been shared with license-free error-tolerant communications applications such as wireless LANs and cordless phones in the 915 MHz, 2450 MHz, and 5800 MHz bands. Because licensed devices already are required to be tolerant of ISM emissions in these bands, unlicensed low power uses are generally able to operate in these bands without causing problems for licensed uses. Note that the 915 MHz band should not be used in countries outside Region 2, except those that specifically allow it such as Australia and Israel, especially those that use the GSM-900 band for cellphones.

Wireless LAN usage

Bluetooth 2450 MHz band

HIPERLAN 5800 MHz band

IEEE 802.11 2450 MHz and 5800 MHz bands

Wireless LANs and cordless phones can also use frequency bands other than the ISM bands, but such uses require approval on a country by country basis. DECT phones use allocated spectrum outside the ISM bands that differs in Europe and North America. Ultra-wideband LANs require more spectrum than the ISM bands can provide, so the relevant standards such as IEEE 802.15.4 are designed to make use of spectrum outside the ISM bands. Despite the fact that these additional bands are outside the official ITU-R ISM bands, because they are used for the same types of low power personal communications, these additional frequency bands are sometimes referred to as ISM bands as well.

Also note that the 'Spektrum' brand of radio control equipment, uses the 2.4 GHz band range for low power remote control of toys, from gas powered cars to miniature aircraft.

• Fixed Wireless Data

• 900 MHz vs. 2.4 GHz
• Cordless phone frequencies
• ITU page on definitions of ISM bands
• ITU page on Radio Regulations
• European Radiocommunications Office frequency information system
• In the US, CFR Title 47 Part 18 describes the regulation of the ISM bands. Part 15 Subpart 247 contains regulations for wireless LAN devices operating in the ISM bands.