This review paper illustrates the different SQUID based systems used for bi
omagnetic imaging. The review is divided into nine sections. The first thre
e sections are introductory: section 1 is a short overview of the topic; se
ction 2 summarizes how the biomagnetic fields are generated and what are th
e basic mathematical models for the field sources; section 3 illustrates th
e principles of operation of the SQUID device. Sections 4-8 are specificall
y devoted to the description of the different systems used for biomagnetic
measurements: section 4 discusses the different types of detection coils; s
ection 5 illustrates the SQUID sensors specifically designed for biomagneti
c applications together with the necessary driving electronics, with specia
l emphasis on high-temperature superconductivity (HTS) SQUIDS, since HTS de
vices are still in a developing stage; section 6 illustrates the different
noise reduction techniques; section 7 describes the different multichannel
sensors presently operating; and, finally, section 8 gives a hint of what k
ind of physiological and/or clinical information may be gathered by the bio
magnetic technique. Section 9 suggests some future trends for the biomagnet
ic technique.