Extremely sharp magnetic transitions from the superconducting to the normal state are found for highly purified tantalum specimens with residual resistivities approaching 1×10-3 μ ohm cm. Negligible flux trapping and pronounced supercooling is found to occur in these samples near the transition temperature Tc. Values of Tc as high as 4.483A°K±.002A°K and of the critical field at 0A°K, H0, as low as 830±8 gauss were found for these specimens. The critical field curve is found to have a maximum deviation from a parabolic temperature dependence of about 3%. For tantalum the transition temperature decreases with increasing residual resistivity in much the same way as that observed by Serin and co-workers in dilute substitutional alloys. Some investigation is made of the current dependence of the resistance transition in a magnetic field. © 1960 The American Physical Society.