We present H i data cubes of four low–luminosity early–type ( E/S0 and S0 ) galaxies which are currently forming stars .
These galaxies have absolute magnitudes in the range M _ { B } = -17.9 to -19.9 ( H _ { \circ } = 50 km s ^ { -1 } Mpc ^ { -1 } ) .
Their H i masses range between a few times 10 ^ { 8 } and a few times 10 ^ { 9 } M _ { \odot } and the corresponding values for M _ { HI } / L _ { B } are between 0.07 and 0.42 , so these systems are H i rich for their morphological type .
In all four galaxies , the H i is strongly centrally concentrated with high central H i surface densities , in contrast to what is typically observed in more luminous early–type galaxies .
Star formation is occurring only in the central regions . In two galaxies ( NGC 802 and ESO 118–G34 ) , the kinematics of the H i suggests that the gas is in a strongly warped disk , which we take as evidence for recent accretion of H i .
In the other two galaxies ( NGC 2328 and ESO 027–G21 ) the H i must have been part of the systems for a considerable time .
The H i properties of low–luminosity early–type galaxies appear to be systematically different from those of many more luminous early–type galaxies , and we suggest that these differences are due to a different evolution of the two classes .

The star formation history of these galaxies remains unclear .
Their UBV colours and H \alpha emission–line strengths are consistent with having formed stars at a slowly–declining rate for most of the past 10 ^ { 10 } years .
If so , their star formation history would be intermediate between late–type spiral disks and giant ellipticals .
However , the current data do not rule out a small burst of recent star formation overlaid on an older stellar population .

Three of the galaxies have weak radio continuum emission , and the ratio of the far–infrared ( FIR ) to radio–continuum emission is very similar to that of spirals of similar FIR- or radio luminosity .
We find that , except in the largest galaxy observed , the radio–continuum emission can be accounted for solely by thermal ( free–free ) emission from H ii regions , with no non–thermal ( synchrotron ) disk component .
Thus , although these galaxies have gaseous disks , a disk magnetic field may be very weak or absent .