1. Data on body weight, fat score and length of stopover of Palaearctic passerine migrants trapped at two sites in the central Algerian Sahara in autumn 1983 are presented. 2. Birds found grounded in oases were in good condition. They were not critically short of fat reserves. 3. Some of the migrant species found there have probably terminated their migration whereas other species do only stopover for fattening and do in fact continue their migration if they have restored sufficient fat for a further flight. 4. The daily activity pattern of caged migrants depended on their fat reserves. 5. The available food supplies were high enough for fattening.